diff --git a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/AttachmentHelper.java b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/AttachmentHelper.java
index b9748f936c..3c4652ee00 100644
--- a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/AttachmentHelper.java
+++ b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/AttachmentHelper.java
@@ -14,64 +14,44 @@
 package org.eclipse.equinox.internal.p2.director;
 
 import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 import org.eclipse.equinox.p2.metadata.*;
 import org.eclipse.equinox.p2.query.QueryUtil;
 
 public class AttachmentHelper {
 	private static final IInstallableUnitFragment[] NO_FRAGMENTS = new IInstallableUnitFragment[0];
 
-	public static Collection<IInstallableUnit> attachFragments(Iterator<IInstallableUnit> toAttach, Map<IInstallableUnitFragment, List<IInstallableUnit>> fragmentsToIUs) {
+	public static Collection<IInstallableUnit> attachFragments(Stream<IInstallableUnit> toAttach,
+			Map<IInstallableUnitFragment, List<IInstallableUnit>> fragmentsToIUs) {
 		Map<IInstallableUnit, IInstallableUnitFragment[]> fragmentBindings = new HashMap<>();
 		//Build a map inverse of the one provided in input (host --> List of fragments)
 		Map<IInstallableUnit, List<IInstallableUnitFragment>> iusToFragment = new HashMap<>(fragmentsToIUs.size());
-		for (Map.Entry<IInstallableUnitFragment, List<IInstallableUnit>> mapping : fragmentsToIUs.entrySet()) {
-			IInstallableUnitFragment fragment = mapping.getKey();
-			List<IInstallableUnit> existingMatches = mapping.getValue();
-
+		fragmentsToIUs.forEach((fragment, existingMatches) -> {
 			for (IInstallableUnit host : existingMatches) {
-				List<IInstallableUnitFragment> potentialFragments = iusToFragment.get(host);
-				if (potentialFragments == null) {
-					potentialFragments = new ArrayList<>();
-					iusToFragment.put(host, potentialFragments);
-				}
-				potentialFragments.add(fragment);
+				iusToFragment.computeIfAbsent(host, h -> new ArrayList<>()).add(fragment);
 			}
-		}
+		});
 
-		for (Map.Entry<IInstallableUnit, List<IInstallableUnitFragment>> entry : iusToFragment.entrySet()) {
-			IInstallableUnit hostIU = entry.getKey();
-			List<IInstallableUnitFragment> potentialIUFragments = entry.getValue();
-			ArrayList<IInstallableUnitFragment> applicableFragments = new ArrayList<>();
+		iusToFragment.forEach((hostIU, potentialIUFragments) -> {
+			List<IInstallableUnitFragment> applicableFragments = new ArrayList<>();
 			for (IInstallableUnitFragment potentialFragment : potentialIUFragments) {
-				if (hostIU.equals(potentialFragment))
+				if (hostIU.equals(potentialFragment)) {
 					continue;
-
+				}
 				// Check to make sure the host meets the requirements of the fragment
 				Collection<IRequirement> reqsFromFragment = potentialFragment.getHost();
-				boolean match = true;
-				boolean requirementMatched = false;
-				for (Iterator<IRequirement> iterator = reqsFromFragment.iterator(); iterator.hasNext() && match == true;) {
-					IRequirement reqs = iterator.next();
-					requirementMatched = false;
-					if (hostIU.satisfies(reqs))
-						requirementMatched = true;
-					if (requirementMatched == false) {
-						match = false;
-						break;
-					}
-
-				}
-				if (match) {
+				if (reqsFromFragment.stream().allMatch(hostIU::satisfies)) {
 					applicableFragments.add(potentialFragment);
 				}
 			}
 
 			IInstallableUnitFragment theFragment = null;
 			int specificityLevel = 0;
-			LinkedList<IInstallableUnitFragment> fragments = new LinkedList<>();
+			Deque<IInstallableUnitFragment> fragments = new LinkedList<>();
 			for (IInstallableUnitFragment fragment : applicableFragments) {
 				if (isTranslation(fragment)) {
-					fragments.add(fragment);
+					fragments.addLast(fragment);
 					continue;
 				}
 				if (fragment.getHost().size() > specificityLevel) {
@@ -79,29 +59,23 @@ public static Collection<IInstallableUnit> attachFragments(Iterator<IInstallable
 					specificityLevel = fragment.getHost().size();
 				}
 			}
-			if (theFragment != null)
+			if (theFragment != null) {
 				fragments.addFirst(theFragment);
-			if (!fragments.isEmpty())
-				fragmentBindings.put(hostIU, fragments.toArray(new IInstallableUnitFragment[fragments.size()]));
-		}
+			}
+			if (!fragments.isEmpty()) {
+				fragmentBindings.put(hostIU, fragments.toArray(IInstallableUnitFragment[]::new));
+			}
+		});
 		//build the collection of resolved IUs
-		Collection<IInstallableUnit> result = new HashSet<>();
-		while (toAttach.hasNext()) {
-			IInstallableUnit iu = toAttach.next();
-			if (iu == null)
-				continue;
+		return toAttach.filter(Objects::nonNull).map(iu -> {
 			//just return fragments as they are
 			if (QueryUtil.isFragment(iu)) {
-				result.add(iu);
-				continue;
+				return iu;
 			}
 			//return a new IU that combines the IU with its bound fragments
-			IInstallableUnitFragment[] fragments = fragmentBindings.get(iu);
-			if (fragments == null)
-				fragments = NO_FRAGMENTS;
-			result.add(MetadataFactory.createResolvedInstallableUnit(iu, fragments));
-		}
-		return result;
+			IInstallableUnitFragment[] fragments = fragmentBindings.getOrDefault(iu, NO_FRAGMENTS);
+			return (MetadataFactory.createResolvedInstallableUnit(iu, fragments));
+		}).collect(Collectors.toSet());
 	}
 
 	private static boolean isTranslation(IInstallableUnitFragment fragment) {
diff --git a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/OptimizationFunction.java b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/OptimizationFunction.java
index 42672c6e9a..e6139038c3 100644
--- a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/OptimizationFunction.java
+++ b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/OptimizationFunction.java
@@ -48,7 +48,7 @@ public List<WeightedObject<? extends Object>> createOptimizationFunction(IInstal
 		if (newRoots.isEmpty()) {
 			transitiveClosure = Collections.emptySet();
 		} else {
-			IQueryable<IInstallableUnit> queryable = new Slicer(picker, selectionContext, false).slice(newRoots.toArray(new IInstallableUnit[newRoots.size()]), new NullProgressMonitor());
+			IQueryable<IInstallableUnit> queryable = new Slicer(picker, selectionContext, false).slice(newRoots, null);
 			if (queryable == null) {
 				transitiveClosure = Collections.emptySet();
 			} else {
diff --git a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/PermissiveSlicer.java b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/PermissiveSlicer.java
index 2e0eb45a46..15eaf2b93a 100644
--- a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/PermissiveSlicer.java
+++ b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/PermissiveSlicer.java
@@ -17,6 +17,7 @@
 import org.eclipse.equinox.internal.p2.metadata.RequiredCapability;
 import org.eclipse.equinox.p2.metadata.IInstallableUnit;
 import org.eclipse.equinox.p2.metadata.IRequirement;
+import org.eclipse.equinox.p2.metadata.expression.IMatchExpression;
 import org.eclipse.equinox.p2.query.IQueryable;
 
 public class PermissiveSlicer extends Slicer {
@@ -29,7 +30,7 @@ public class PermissiveSlicer extends Slicer {
 
 	public PermissiveSlicer(IQueryable<IInstallableUnit> input, Map<String, String> context, boolean includeOptionalDependencies, boolean everythingGreedy, boolean evalFilterTo, boolean considerOnlyStrictDependency, boolean onlyFilteredRequirements) {
 		super(input, context, true);
-		this.considerFilter = (context != null && context.size() > 1) ? true : false;
+		this.considerFilter = context != null && context.size() > 1;
 		this.includeOptionalDependencies = includeOptionalDependencies;
 		this.everythingGreedy = everythingGreedy;
 		this.evalFilterTo = evalFilterTo;
@@ -39,45 +40,31 @@ public PermissiveSlicer(IQueryable<IInstallableUnit> input, Map<String, String>
 
 	@Override
 	protected boolean isApplicable(IInstallableUnit iu) {
-		if (considerFilter)
+		if (considerFilter) {
 			return super.isApplicable(iu);
-		if (iu.getFilter() == null)
-			return true;
-		return evalFilterTo;
+		}
+		return iu.getFilter() == null || evalFilterTo;
 	}
 
 	@Override
 	protected boolean isApplicable(IRequirement req) {
 		//Every filter in this method needs to continue except when the filter does not pass
-		if (!includeOptionalDependencies)
-			if (req.getMin() == 0)
-				return false;
-
-		if (considerOnlyStrictDependency) {
-			if (!RequiredCapability.isStrictVersionRequirement(req.getMatches()))
-				return false;
+		if (!includeOptionalDependencies && req.getMin() == 0) {
+			return false;
 		}
-
-		//deal with filters
-		if (considerFilter) {
-			if (onlyFilteredRequirements && req.getFilter() == null) {
-				return false;
-			}
-			return super.isApplicable(req);
+		if (considerOnlyStrictDependency && !RequiredCapability.isStrictVersionRequirement(req.getMatches())) {
+			return false;
 		}
-		if (req.getFilter() == null) {
-			if (onlyFilteredRequirements)
-				return false;
-			return true;
+		//deal with filters
+		IMatchExpression<IInstallableUnit> filter = req.getFilter();
+		if (filter == null) {
+			return !onlyFilteredRequirements;
 		}
-		return evalFilterTo;
+		return considerFilter ? filter.isMatch(selectionContext) : evalFilterTo;
 	}
 
 	@Override
 	protected boolean isGreedy(IRequirement req) {
-		if (everythingGreedy) {
-			return true;
-		}
-		return super.isGreedy(req);
+		return everythingGreedy || super.isGreedy(req);
 	}
 }
diff --git a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/SimplePlanner.java b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/SimplePlanner.java
index f06d4ea241..0541226c54 100644
--- a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/SimplePlanner.java
+++ b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/SimplePlanner.java
@@ -23,7 +23,6 @@
 import static org.eclipse.equinox.internal.provisional.p2.director.RequestStatus.REMOVED;
 
 import java.lang.reflect.Method;
-import java.net.URI;
 import java.util.*;
 import java.util.stream.Stream;
 import org.eclipse.core.runtime.*;
@@ -47,7 +46,7 @@
 import org.eclipse.osgi.util.NLS;
 
 public class SimplePlanner implements IPlanner {
-	private static boolean DEBUG = Tracing.DEBUG_PLANNER_OPERANDS;
+	private static final boolean DEBUG = Tracing.DEBUG_PLANNER_OPERANDS;
 
 	private static final int ExpandWork = 12;
 	private static final String INCLUDE_PROFILE_IUS = "org.eclipse.equinox.p2.internal.profileius"; //$NON-NLS-1$
@@ -156,15 +155,12 @@ private static IStatus convertExplanationToStatus(Set<Explanation> explanations)
 		// for the PDE target platform into a general purpose profile.
 		List<IStatus> forTargets = new ArrayList<>(0);
 		for (Explanation next : explanations) {
-			if (next instanceof MissingIU) {
-				MissingIU missingIU = (MissingIU) next;
-				if (missingIU.req instanceof IRequiredCapability
-						&& missingIU.req.getMatches().getParameters().length == 3
-						&& "A.PDE.Target.Platform".equals(((IRequiredCapability) missingIU.req).getNamespace())) {//$NON-NLS-1$
-					// This IU requires the PDE target platform IU and it is missing.
-					// I.e. this IU is intended only for the PDE target platform.
-					forTargets.add(Status.error(Explanation.getUserReadableName(missingIU.iu)));
-				}
+			if (next instanceof MissingIU missingIU && missingIU.req instanceof IRequiredCapability requiredCapability
+					&& requiredCapability.getMatches().getParameters().length == 3
+					&& "A.PDE.Target.Platform".equals(requiredCapability.getNamespace())) {//$NON-NLS-1$
+				// This IU requires the PDE target platform IU and it is missing.
+				// I.e. this IU is intended only for the PDE target platform.
+				forTargets.add(Status.error(Explanation.getUserReadableName(missingIU.iu)));
 			}
 		}
 		if (!forTargets.isEmpty()) {
@@ -219,19 +215,11 @@ private static IStatus convertChangesToStatus(Map<IInstallableUnit, RequestStatu
 	}
 
 	private static IStatus buildChangeStatus(RequestStatus rs) {
-		final String change;
-		switch (rs.getInitialRequestType()) {
-		case ADDED:
-			change = "Add"; //$NON-NLS-1$
-			break;
-		case REMOVED:
-			change = "Remove"; //$NON-NLS-1$
-			break;
-		default:
-			change = "UNKNOWN change type " + rs.getInitialRequestType(); //$NON-NLS-1$
-			break;
-		}
-
+		final String change = switch (rs.getInitialRequestType()) {
+		case ADDED -> "Add"; //$NON-NLS-1$
+		case REMOVED -> "Remove"; //$NON-NLS-1$
+		default -> "UNKNOWN change type " + rs.getInitialRequestType(); //$NON-NLS-1$
+		};
 		final IStatus status;
 		if (!rs.isOK()) {
 			String message = NLS.bind(Messages.Director_Unsatisfied_Change, change,
@@ -366,10 +354,8 @@ private Collection<IInstallableUnit> gatherAvailableInstallableUnits(List<IInsta
 	}
 
 	private static boolean hasHigherFidelity(IInstallableUnit iu, IInstallableUnit currentIU) {
-		if (Boolean.parseBoolean(currentIU.getProperty(IInstallableUnit.PROP_PARTIAL_IU))
-				&& !Boolean.parseBoolean(iu.getProperty(IInstallableUnit.PROP_PARTIAL_IU)))
-			return true;
-		return false;
+		return Boolean.parseBoolean(currentIU.getProperty(IInstallableUnit.PROP_PARTIAL_IU))
+				&& !Boolean.parseBoolean(iu.getProperty(IInstallableUnit.PROP_PARTIAL_IU));
 	}
 
 	public SimplePlanner(IProvisioningAgent agent) {
@@ -382,12 +368,11 @@ public SimplePlanner(IProvisioningAgent agent) {
 	}
 
 	private boolean satisfyMetaRequirements(Map<String, String> props) {
-		if (props == null)
-			return true;
-		if (props.get(CONSIDER_METAREQUIREMENTS) == null
-				|| "true".equalsIgnoreCase(props.get(CONSIDER_METAREQUIREMENTS))) //$NON-NLS-1$
+		if (props == null) {
 			return true;
-		return false;
+		}
+		return props.get(CONSIDER_METAREQUIREMENTS) == null
+				|| Boolean.parseBoolean(props.get(CONSIDER_METAREQUIREMENTS));
 	}
 
 	private boolean satisfyMetaRequirements(IProfile p) {
@@ -429,8 +414,8 @@ private Object getSolutionFor(ProfileChangeRequest profileChangeRequest, Provisi
 					sub.newChild(ExpandWork / 4));
 			Slicer slicer = new Slicer(new QueryableArray(availableIUs), newSelectionContext,
 					satisfyMetaRequirements(profileChangeRequest.getProfileProperties()));
-			IQueryable<IInstallableUnit> slice = slicer
-					.slice(new IInstallableUnit[] { (IInstallableUnit) updatedPlan[0] }, sub.newChild(ExpandWork / 4));
+			IQueryable<IInstallableUnit> slice = slicer.slice(List.of((IInstallableUnit) updatedPlan[0]),
+					sub.newChild(ExpandWork / 4));
 			if (slice == null) {
 				IProvisioningPlan plan = engine.createPlan(profile, context);
 				plan.setStatus(slicer.getStatus());
@@ -468,8 +453,8 @@ private Object getSolutionFor(ProfileChangeRequest profileChangeRequest, Provisi
 				IStatus explanationStatus = convertExplanationToStatus(explanation);
 
 				Map<IInstallableUnit, RequestStatus>[] changes = buildDetailedErrors(profileChangeRequest);
-				Map<IInstallableUnit, RequestStatus> requestChanges = (changes == null) ? null : changes[0];
-				Map<IInstallableUnit, RequestStatus> requestSideEffects = (changes == null) ? null : changes[1];
+				Map<IInstallableUnit, RequestStatus> requestChanges = changes[0];
+				Map<IInstallableUnit, RequestStatus> requestSideEffects = changes[1];
 				PlannerStatus plannerStatus = new PlannerStatus(explanationStatus,
 						new RequestStatus(null, REMOVED, ERROR, explanation), requestChanges, requestSideEffects, null);
 
@@ -508,16 +493,15 @@ public IProvisioningPlan getProvisioningPlan(IProfileChangeRequest request, Prov
 			// Get the solution for the initial request
 			Object resolutionResult = getSolutionFor(pcr, context, sub.newChild(ExpandWork / 2));
 			// a return value of a plan indicates failure when resolving so return.
-			if (resolutionResult instanceof IProvisioningPlan) {
-				return (IProvisioningPlan) resolutionResult;
+			if (resolutionResult instanceof IProvisioningPlan plan) {
+				return plan;
 			}
 
 			Projector projector = (Projector) resolutionResult;
 			Collection<IInstallableUnit> newState = projector.extractSolution();
 			Collection<IInstallableUnit> fullState = new ArrayList<>();
 			fullState.addAll(newState);
-			newState = AttachmentHelper.attachFragments(newState.iterator(),
-					projector.getFragmentAssociation());
+			newState = AttachmentHelper.attachFragments(newState.stream(), projector.getFragmentAssociation());
 
 			IProvisioningPlan temporaryPlan = generatePlan(projector, newState, pcr, context);
 			projector.close();
@@ -646,8 +630,10 @@ private IProvisioningPlan createInstallerPlan(IProfile profile, ProfileChangeReq
 			}
 
 			if (satisfyMetaRequirements(profile) && !profile.getProfileId().equals(installerProfile.getProfileId())) {
-				return createInstallerPlanForCohostedCaseFromExternalInstaller(profile, initialRequest, initialPlan,
-						expectedState, initialContext, installerProfile, sub);
+				// co-hosted case from external installer
+				IProvisioningPlan planForProfile = generatePlan(null, expectedState, initialRequest, initialContext);
+				return createInstallerPlanForExternalInstaller(profile, initialRequest, planForProfile, expectedState,
+						initialContext, installerProfile, sub);
 			}
 
 			return createInstallerPlanForExternalInstaller(profile, initialRequest, initialPlan, expectedState,
@@ -670,14 +656,6 @@ private boolean haveSameLocation(IProvisioningAgent agent1, IProvisioningAgent a
 		return thisLocation.getRootLocation().equals(otherLocation.getRootLocation());
 	}
 
-	private IProvisioningPlan createInstallerPlanForCohostedCaseFromExternalInstaller(IProfile profile,
-			ProfileChangeRequest initialRequest, IProvisioningPlan initialPlan, Collection<IInstallableUnit> newState,
-			ProvisioningContext initialContext, IProfile agentProfile, SubMonitor sub) {
-		IProvisioningPlan planForProfile = generatePlan(null, newState, initialRequest, initialContext);
-		return createInstallerPlanForExternalInstaller(profile, initialRequest, planForProfile, newState,
-				initialContext, agentProfile, sub);
-	}
-
 	// Deal with the case where the agent profile is different than the one being
 	// provisioned
 	private IProvisioningPlan createInstallerPlanForExternalInstaller(IProfile targetedProfile,
@@ -702,12 +680,12 @@ private IProvisioningPlan createInstallerPlanForExternalInstaller(IProfile targe
 		agentRequest.add(actionsIU);
 		if (previousActionsIU != null)
 			agentRequest.remove(previousActionsIU);
-		Object externalInstallerPlan = getSolutionFor(agentRequest, initialContext, sub.newChild(10));
-		if (externalInstallerPlan instanceof IProvisioningPlan
-				&& ((IProvisioningPlan) externalInstallerPlan).getStatus().getSeverity() == ERROR) {
+		Object externalInstallerPlan = getSolutionFor(agentRequest, initialContext, sub.split(10));
+		if (externalInstallerPlan instanceof IProvisioningPlan provPlan
+				&& provPlan.getStatus().getSeverity() == ERROR) {
 			MultiStatus externalInstallerStatus = new MultiStatus(PI_DIRECTOR, 0, Messages.Planner_can_not_install_preq,
 					null);
-			externalInstallerStatus.add(((IProvisioningPlan) externalInstallerPlan).getStatus());
+			externalInstallerStatus.add(provPlan.getStatus());
 			IProvisioningPlan plan = engine.createPlan(initialRequest.getProfile(), initialContext);
 			plan.setStatus(externalInstallerStatus);
 			IProvisioningPlan installerPlan = engine.createPlan(agentProfile, initialContext);
@@ -728,7 +706,7 @@ private IProvisioningPlan createInstallerPlanForExternalInstaller(IProfile targe
 	private IProvisioningPlan createInstallerPlanForCohostedCase(IProfile profile, ProfileChangeRequest initialRequest,
 			IProvisioningPlan initialPlan, Collection<IInstallableUnit> unattachedState,
 			Collection<IInstallableUnit> expectedState, ProvisioningContext initialContext, SubMonitor monitor) {
-		Collection<IRequirement> metaRequirements = initialRequest.getRemovals().size() == 0
+		Collection<IRequirement> metaRequirements = initialRequest.getRemovals().isEmpty()
 				? areMetaRequirementsSatisfied(profile, expectedState, initialPlan)
 				: extractMetaRequirements(expectedState, initialPlan);
 		if (metaRequirements == null || metaRequirements.isEmpty())
@@ -749,28 +727,26 @@ private IProvisioningPlan createInstallerPlanForCohostedCase(IProfile profile, P
 		for (String removedPropertie : removedProperties) {
 			agentRequest.removeProfileProperty(removedPropertie);
 		}
-		Map<IInstallableUnit, List<String>> removedIUProperties = initialRequest
-				.getInstallableUnitProfilePropertiesToRemove();
-		for (Map.Entry<IInstallableUnit, List<String>> entry : removedIUProperties.entrySet()) {
-			for (String propKey : entry.getValue()) {
-				agentRequest.removeInstallableUnitProfileProperty(entry.getKey(), propKey);
+		initialRequest.getInstallableUnitProfilePropertiesToRemove().forEach((iu, propertyKeys) -> {
+			for (String propKey : propertyKeys) {
+				agentRequest.removeInstallableUnitProfileProperty(iu, propKey);
 			}
-		}
+		});
 
 		if (previousMetaRequirementIU != null)
 			agentRequest.remove(previousMetaRequirementIU);
 		agentRequest.add(metaRequirementIU);
 
 		ProvisioningContext agentCtx = new ProvisioningContext(agent);
-		agentCtx.setMetadataRepositories(new URI[0]);
-		ArrayList<IInstallableUnit> extraIUs = new ArrayList<>(unattachedState);
+		agentCtx.setMetadataRepositories();
+		List<IInstallableUnit> extraIUs = new ArrayList<>(unattachedState);
 		agentCtx.setExtraInstallableUnits(extraIUs);
 		Object agentSolution = getSolutionFor(agentRequest, agentCtx, monitor.newChild(3));
-		if (agentSolution instanceof IProvisioningPlan
-				&& ((IProvisioningPlan) agentSolution).getStatus().getSeverity() == ERROR) {
+		if (agentSolution instanceof IProvisioningPlan solutionPlan
+				&& solutionPlan.getStatus().getSeverity() == ERROR) {
 			MultiStatus agentStatus = new MultiStatus(PI_DIRECTOR, 0,
 					Messages.Planner_actions_and_software_incompatible, null);
-			agentStatus.add(((IProvisioningPlan) agentSolution).getStatus());
+			agentStatus.add(solutionPlan.getStatus());
 			IProvisioningPlan plan = engine.createPlan(initialRequest.getProfile(), initialContext);
 			plan.setStatus(agentStatus);
 			IProvisioningPlan installerPlan = engine.createPlan(initialRequest.getProfile(), initialContext);
@@ -783,7 +759,7 @@ private IProvisioningPlan createInstallerPlanForCohostedCase(IProfile profile, P
 		// the profile and the solution we just computed
 		Collection<IInstallableUnit> agentState = ((Projector) agentSolution).extractSolution();
 		agentState.remove(metaRequirementIU); // Remove the fake IU
-		agentState = AttachmentHelper.attachFragments(agentState.iterator(),
+		agentState = AttachmentHelper.attachFragments(agentState.stream(),
 				((Projector) agentSolution).getFragmentAssociation());
 
 		ProvisioningContext noRepoContext = createNoRepoContext(initialRequest);
@@ -791,14 +767,13 @@ private IProvisioningPlan createInstallerPlanForCohostedCase(IProfile profile, P
 		Object initialSolution = getSolutionFor(
 				new ProfileChangeRequest(new EverythingOptionalProfile(initialRequest.getProfile())), noRepoContext,
 				new NullProgressMonitor());
-		if (initialSolution instanceof IProvisioningPlan) {
+		if (initialSolution instanceof IProvisioningPlan plan) {
 			LogHelper.log(Status.error("The resolution of the previous state contained in profile " //$NON-NLS-1$
 					+ initialRequest.getProfile().getProfileId() + " version " //$NON-NLS-1$
 					+ initialRequest.getProfile().getTimestamp() + " failed.")); //$NON-NLS-1$
-			return (IProvisioningPlan) initialSolution;
+			return plan;
 		}
-		Iterator<IInstallableUnit> profileState = initialRequest.getProfile().query(QueryUtil.createIUAnyQuery(), null)
-				.iterator();
+		var profileState = initialRequest.getProfile().query(QueryUtil.createIUAnyQuery(), null).stream();
 		Collection<IInstallableUnit> initialState = AttachmentHelper.attachFragments(profileState,
 				((Projector) initialSolution).getFragmentAssociation());
 
@@ -816,7 +791,7 @@ private IProvisioningPlan generatePlan(Projector newSolution, Collection<IInstal
 		// Compute the attachment of the new state if not provided
 		if (newState == null) {
 			newState = newSolution.extractSolution();
-			newState = AttachmentHelper.attachFragments(newState.iterator(), newSolution.getFragmentAssociation());
+			newState = AttachmentHelper.attachFragments(newState.stream(), newSolution.getFragmentAssociation());
 		}
 		ProvisioningContext noRepoContext = createNoRepoContext(request);
 
@@ -824,14 +799,13 @@ private IProvisioningPlan generatePlan(Projector newSolution, Collection<IInstal
 		Object initialSolution = getSolutionFor(
 				new ProfileChangeRequest(new EverythingOptionalProfile(request.getProfile())), noRepoContext,
 				new NullProgressMonitor());
-		if (initialSolution instanceof IProvisioningPlan) {
+		if (initialSolution instanceof IProvisioningPlan plan) {
 			LogHelper.log(Status.error(
 					"The resolution of the previous state contained in profile " + request.getProfile().getProfileId() //$NON-NLS-1$
 							+ " version " + request.getProfile().getTimestamp() + " failed.")); //$NON-NLS-1$//$NON-NLS-2$
-			return (IProvisioningPlan) initialSolution;
+			return plan;
 		}
-		Iterator<IInstallableUnit> profileState = request.getProfile().query(QueryUtil.createIUAnyQuery(), null)
-				.iterator();
+		Stream<IInstallableUnit> profileState = request.getProfile().query(QueryUtil.createIUAnyQuery(), null).stream();
 		Collection<IInstallableUnit> initialState = AttachmentHelper.attachFragments(profileState,
 				((Projector) initialSolution).getFragmentAssociation());
 
@@ -841,8 +815,8 @@ private IProvisioningPlan generatePlan(Projector newSolution, Collection<IInstal
 
 	private ProvisioningContext createNoRepoContext(ProfileChangeRequest request) {
 		ProvisioningContext noRepoContext = new ProvisioningContext(agent);
-		noRepoContext.setMetadataRepositories(new URI[0]);
-		noRepoContext.setArtifactRepositories(new URI[0]);
+		noRepoContext.setMetadataRepositories();
+		noRepoContext.setArtifactRepositories();
 		noRepoContext.setProperty(INCLUDE_PROFILE_IUS, Boolean.FALSE.toString());
 		noRepoContext.setExtraInstallableUnits(new ArrayList<>(request.getProfile()
 				.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()).toUnmodifiableSet()));
@@ -868,14 +842,13 @@ private IInstallableUnit createIUForMetaRequirements(IProfile profile, Collectio
 		description.setVersion(version);
 		description.addRequirements(metaRequirements);
 
-		ArrayList<IProvidedCapability> providedCapabilities = new ArrayList<>();
+		List<IProvidedCapability> providedCapabilities = new ArrayList<>();
 		IProvidedCapability providedCapability = MetadataFactory
 				.createProvidedCapability(IInstallableUnit.NAMESPACE_IU_ID, id, version);
 		providedCapabilities.add(providedCapability);
 		description.addProvidedCapabilities(providedCapabilities);
 
-		IInstallableUnit actionsIU = MetadataFactory.createInstallableUnit(description);
-		return actionsIU;
+		return MetadataFactory.createInstallableUnit(description);
 	}
 
 	private IInstallableUnit createIURepresentingTheProfile(Set<IRequirement> allRequirements) {
@@ -908,7 +881,7 @@ private Object[] updatePlannerInfo(ProfileChangeRequest profileChangeRequest, Pr
 		}
 		// Remove the iu properties associated to the ius removed and the iu properties
 		// being removed as well
-		if (removalRequested.size() != 0) {
+		if (!removalRequested.isEmpty()) {
 			for (Iterator<IInstallableUnit> iterator = alreadyInstalled.iterator(); iterator.hasNext();) {
 				IInstallableUnit iu = iterator.next();
 				for (IInstallableUnit removed : removalRequested) {
diff --git a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/Slicer.java b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/Slicer.java
index b751aacc55..cfbad1cc07 100644
--- a/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/Slicer.java
+++ b/bundles/org.eclipse.equinox.p2.director/src/org/eclipse/equinox/internal/p2/director/Slicer.java
@@ -31,42 +31,42 @@ public class Slicer {
 	private final IQueryable<IInstallableUnit> possibilites;
 	private final boolean considerMetaRequirements;
 	protected final IInstallableUnit selectionContext;
-	private final Map<String, Map<Version, IInstallableUnit>> slice; //The IUs that have been considered to be part of the problem
-	private final MultiStatus result;
+	/** The IUs that have been considered to be part of the problem */
+	private final Map<String, Map<Version, IInstallableUnit>> slice = new HashMap<>();
+	private final MultiStatus result = new MultiStatus(Slicer.class, 0, Messages.Planner_Problems_resolving_plan);
 
-	private LinkedList<IInstallableUnit> toProcess;
-	private Set<IInstallableUnit> considered; //IUs to add to the slice
-	private Set<IInstallableUnit> nonGreedyIUs = new HashSet<>(); //IUs that are brought in by non greedy dependencies
+	private Queue<IInstallableUnit> toProcess;
+	private Set<IInstallableUnit> considered; // IUs to add to the slice
+	private final Set<IInstallableUnit> nonGreedyIUs = new HashSet<>(); // IUs that are brought in by non greedy dependencies
 
 	public Slicer(IQueryable<IInstallableUnit> input, Map<String, String> context, boolean considerMetaRequirements) {
 		this(input, InstallableUnit.contextIU(context), considerMetaRequirements);
 	}
 
-	public Slicer(IQueryable<IInstallableUnit> possibilites, IInstallableUnit selectionContext, boolean considerMetaRequirements) {
+	public Slicer(IQueryable<IInstallableUnit> possibilites, IInstallableUnit selectionContext,
+			boolean considerMetaRequirements) {
 		this.possibilites = possibilites;
 		this.selectionContext = selectionContext;
 		this.considerMetaRequirements = considerMetaRequirements;
-		slice = new HashMap<>();
-		result = new MultiStatus(DirectorActivator.PI_DIRECTOR, IStatus.OK, Messages.Planner_Problems_resolving_plan, null);
 	}
 
-	public IQueryable<IInstallableUnit> slice(IInstallableUnit[] ius, IProgressMonitor monitor) {
+	public IQueryable<IInstallableUnit> slice(Collection<IInstallableUnit> ius, IProgressMonitor monitor) {
+		monitor = IProgressMonitor.nullSafe(monitor);
 		try {
 			long start = 0;
 			if (DEBUG) {
 				start = System.currentTimeMillis();
 				System.out.println("Start slicing: " + start); //$NON-NLS-1$
 			}
-
 			validateInput(ius);
-			considered = new HashSet<>(Arrays.asList(ius));
+			considered = new HashSet<>(ius);
 			toProcess = new LinkedList<>(considered);
 			while (!toProcess.isEmpty()) {
 				if (monitor.isCanceled()) {
 					result.merge(Status.CANCEL_STATUS);
 					throw new OperationCanceledException();
 				}
-				processIU(toProcess.removeFirst());
+				processIU(toProcess.remove());
 			}
 			computeNonGreedyIUs();
 			if (DEBUG) {
@@ -76,25 +76,26 @@ public IQueryable<IInstallableUnit> slice(IInstallableUnit[] ius, IProgressMonit
 		} catch (IllegalStateException e) {
 			result.add(Status.error(e.getMessage(), e));
 		}
-		if (Tracing.DEBUG && result.getSeverity() != IStatus.OK)
+		if (Tracing.DEBUG && result.getSeverity() != IStatus.OK) {
 			LogHelper.log(result);
-		if (result.getSeverity() == IStatus.ERROR)
+		}
+		if (result.getSeverity() == IStatus.ERROR) {
 			return null;
+		}
 		return new QueryableArray(considered);
 	}
 
 	private void computeNonGreedyIUs() {
 		IQueryable<IInstallableUnit> queryable = new QueryableArray(considered);
-		Iterator<IInstallableUnit> it = queryable.query(QueryUtil.ALL_UNITS, new NullProgressMonitor()).iterator();
-		while (it.hasNext()) {
-			IInstallableUnit iu = it.next().unresolved();
+		for (IInstallableUnit iu : queryable.query(QueryUtil.ALL_UNITS, new NullProgressMonitor())) {
 			Collection<IRequirement> reqs = getRequirements(iu);
 			for (IRequirement req : reqs) {
-				if (!isApplicable(iu, req))
+				if (!isApplicable(iu, req)) {
 					continue;
-
+				}
 				if (!isGreedy(iu, req)) {
-					nonGreedyIUs.addAll(queryable.query(QueryUtil.createMatchQuery(req.getMatches()), null).toUnmodifiableSet());
+					nonGreedyIUs.addAll(
+							queryable.query(QueryUtil.createMatchQuery(req.getMatches()), null).toUnmodifiableSet());
 				}
 			}
 		}
@@ -104,8 +105,9 @@ public MultiStatus getStatus() {
 		return result;
 	}
 
-	//This is a shortcut to simplify the error reporting when the filter of the ius we are being asked to install does not pass
-	private void validateInput(IInstallableUnit[] ius) {
+	// This is a shortcut to simplify the error reporting when the filter of the ius
+	// we are being asked to install does not pass
+	private void validateInput(Collection<IInstallableUnit> ius) {
 		for (IInstallableUnit iu : ius) {
 			if (!isApplicable(iu)) {
 				throw new IllegalStateException(NLS.bind(Messages.Explanation_missingRootFilter, iu));
@@ -131,30 +133,16 @@ protected boolean isApplicable(IInstallableUnit iu) {
 
 	protected void processIU(IInstallableUnit iu) {
 		iu = iu.unresolved();
-
-		Map<Version, IInstallableUnit> iuSlice = slice.get(iu.getId());
-		if (iuSlice == null) {
-
-			iuSlice = new HashMap<>();
-			slice.put(iu.getId(), iuSlice);
-		}
+		Map<Version, IInstallableUnit> iuSlice = slice.computeIfAbsent(iu.getId(), i -> new HashMap<>());
 		iuSlice.put(iu.getVersion(), iu);
 		if (!isApplicable(iu)) {
 			return;
 		}
-
 		Collection<IRequirement> reqs = getRequirements(iu);
-		if (reqs.isEmpty())
-			return;
 		for (IRequirement req : reqs) {
-			if (!isApplicable(iu, req))
-				continue;
-
-			if (!isGreedy(iu, req)) {
-				continue;
+			if (isApplicable(iu, req) && isGreedy(iu, req)) {
+				expandRequirement(iu, req);
 			}
-
-			expandRequirement(iu, req);
 		}
 	}
 
@@ -169,58 +157,58 @@ protected boolean isGreedy(IRequirement req) {
 	private Collection<IRequirement> getRequirements(IInstallableUnit iu) {
 		boolean isPatch = iu instanceof IInstallableUnitPatch;
 		boolean isFragment = iu instanceof IInstallableUnitFragment;
-		//Short-circuit for the case of an IInstallableUnit
-		if ((!isFragment) && (!isPatch) && iu.getMetaRequirements().size() == 0)
+		// Short-circuit for the case of an IInstallableUnit
+		if ((!isFragment) && (!isPatch) && iu.getMetaRequirements().isEmpty()) {
 			return iu.getRequirements();
+		}
 
-		ArrayList<IRequirement> aggregatedRequirements = new ArrayList<>(iu.getRequirements().size() + iu.getMetaRequirements().size() + (isFragment ? ((IInstallableUnitFragment) iu).getHost().size() : 0) + (isPatch ? ((IInstallableUnitPatch) iu).getRequirementsChange().size() : 0));
+		List<IRequirement> aggregatedRequirements = new ArrayList<>(iu.getRequirements().size()
+				+ iu.getMetaRequirements().size() + (isFragment ? ((IInstallableUnitFragment) iu).getHost().size() : 0)
+				+ (isPatch ? ((IInstallableUnitPatch) iu).getRequirementsChange().size() : 0));
 		aggregatedRequirements.addAll(iu.getRequirements());
 
-		if (iu instanceof IInstallableUnitFragment) {
-			aggregatedRequirements.addAll(((IInstallableUnitFragment) iu).getHost());
+		if (iu instanceof IInstallableUnitFragment iuFragment) {
+			aggregatedRequirements.addAll(iuFragment.getHost());
 		}
-
-		if (iu instanceof InstallableUnitPatch) {
-			IInstallableUnitPatch patchIU = (IInstallableUnitPatch) iu;
+		if (iu instanceof InstallableUnitPatch patchIU) {
 			List<IRequirementChange> changes = patchIU.getRequirementsChange();
-			for (IRequirementChange change : changes)
+			for (IRequirementChange change : changes) {
 				aggregatedRequirements.add(change.newValue());
+			}
 		}
-
-		if (considerMetaRequirements)
+		if (considerMetaRequirements) {
 			aggregatedRequirements.addAll(iu.getMetaRequirements());
+		}
 		return aggregatedRequirements;
 	}
 
 	private void expandRequirement(IInstallableUnit iu, IRequirement req) {
-		if (req.getMax() == 0)
+		if (req.getMax() == 0) {
 			return;
+		}
 		IQueryResult<IInstallableUnit> matches = possibilites.query(QueryUtil.createMatchQuery(req.getMatches()), null);
 		int validMatches = 0;
 		for (IInstallableUnit match : matches) {
-			if (!isApplicable(match))
+			if (!isApplicable(match)) {
 				continue;
+			}
 			validMatches++;
 			Map<Version, IInstallableUnit> iuSlice = slice.get(match.getId());
-			if (iuSlice == null || !iuSlice.containsKey(match.getVersion()))
-				consider(match);
+			if ((iuSlice == null || !iuSlice.containsKey(match.getVersion())) && considered.add(match)) {
+				toProcess.add(match);
+			}
 		}
-
 		if (validMatches == 0) {
 			if (req.getMin() == 0) {
-				if (DEBUG)
+				if (DEBUG) {
 					System.out.println("No IU found to satisfy optional dependency of " + iu + " on req " + req); //$NON-NLS-1$//$NON-NLS-2$
+				}
 			} else {
 				result.add(Status.warning(NLS.bind(Messages.Planner_Unsatisfied_dependency, iu, req)));
 			}
 		}
 	}
 
-	private void consider(IInstallableUnit match) {
-		if (considered.add(match))
-			toProcess.addLast(match);
-	}
-
 	Set<IInstallableUnit> getNonGreedyIUs() {
 		return nonGreedyIUs;
 	}
diff --git a/bundles/org.eclipse.equinox.p2.repository.tools/src/org/eclipse/equinox/p2/internal/repository/tools/MirrorApplication.java b/bundles/org.eclipse.equinox.p2.repository.tools/src/org/eclipse/equinox/p2/internal/repository/tools/MirrorApplication.java
index 72ccc01c06..d9762df9a8 100644
--- a/bundles/org.eclipse.equinox.p2.repository.tools/src/org/eclipse/equinox/p2/internal/repository/tools/MirrorApplication.java
+++ b/bundles/org.eclipse.equinox.p2.repository.tools/src/org/eclipse/equinox/p2/internal/repository/tools/MirrorApplication.java
@@ -101,9 +101,7 @@ public Object start(IApplicationContext context) throws Exception {
 	}
 
 	@Override
-	public void stop() {
-		// TODO Auto-generated method stub
-
+	public void stop() { // nothing to do
 	}
 
 	/*
@@ -119,7 +117,7 @@ public void setInitializationData(IConfigurationElement config, String propertyN
 		}
 	}
 
-	public void initializeFromArguments(String[] args) throws Exception {
+	public void initializeFromArguments(String[] args) {
 		if (args == null)
 			return;
 
@@ -323,7 +321,7 @@ private void initializeIUs() throws ProvisionException {
 			while (queryResult.hasNext())
 				sourceIUs.add(queryResult.next());
 			/* old metadata mirroring app did not throw an exception here */
-			if (sourceIUs.size() == 0 && destinationMetadataRepository != null && metadataOrArtifacts == null)
+			if (sourceIUs.isEmpty() && destinationMetadataRepository != null && metadataOrArtifacts == null)
 				throw new ProvisionException(Messages.MirrorApplication_no_IUs);
 		}
 	}
@@ -363,18 +361,19 @@ private IQueryable<IInstallableUnit> performResolution(IProgressMonitor monitor)
 		String profileId = "MirrorApplication-" + System.currentTimeMillis(); //$NON-NLS-1$
 		IProfile profile = registry.addProfile(profileId, slicingOptions.getFilter());
 		IPlanner planner = Activator.getAgent().getService(IPlanner.class);
-		if (planner == null)
+		if (planner == null) {
 			throw new IllegalStateException();
+		}
 		IProfileChangeRequest pcr = planner.createChangeRequest(profile);
 		pcr.addAll(sourceIUs);
 		IProvisioningPlan plan = planner.getProvisioningPlan(pcr, null, monitor);
 		registry.removeProfile(profileId);
-		@SuppressWarnings("unchecked")
-		IQueryable<IInstallableUnit>[] arr = new IQueryable[plan.getInstallerPlan() == null ? 1 : 2];
-		arr[0] = plan.getAdditions();
-		if (plan.getInstallerPlan() != null)
-			arr[1] = plan.getInstallerPlan().getAdditions();
-		return new CompoundQueryable<>(arr);
+		List<IQueryable<IInstallableUnit>> queriables = new ArrayList<>();
+		queriables.add(plan.getAdditions());
+		if (plan.getInstallerPlan() != null) {
+			queriables.add(plan.getInstallerPlan().getAdditions());
+		}
+		return new CompoundQueryable<>(queriables);
 	}
 
 	private IQueryable<IInstallableUnit> slice(IProgressMonitor monitor) throws ProvisionException {
@@ -384,8 +383,7 @@ private IQueryable<IInstallableUnit> slice(IProgressMonitor monitor) throws Prov
 			return performResolution(monitor);
 
 		Slicer slicer = createSlicer(slicingOptions);
-		IQueryable<IInstallableUnit> slice = slicer.slice(sourceIUs.toArray(new IInstallableUnit[sourceIUs.size()]),
-				monitor);
+		IQueryable<IInstallableUnit> slice = slicer.slice(sourceIUs, monitor);
 
 		if (slice != null && slicingOptions.latestVersionOnly()) {
 			IQueryResult<IInstallableUnit> queryResult = slice.query(QueryUtil.createLatestIUQuery(), monitor);
@@ -401,10 +399,9 @@ private IQueryable<IInstallableUnit> slice(IProgressMonitor monitor) throws Prov
 	}
 
 	protected Slicer createSlicer(SlicingOptions options) {
-		PermissiveSlicer slicer = new PermissiveSlicer(getCompositeMetadataRepository(), options.getFilter(),
+		return new PermissiveSlicer(getCompositeMetadataRepository(), options.getFilter(),
 				options.includeOptionalDependencies(), options.isEverythingGreedy(), options.forceFilterTo(),
 				options.considerStrictDependencyOnly(), options.followOnlyFilteredRequirements());
-		return slicer;
 	}
 
 	public void setSlicingOptions(SlicingOptions options) {
diff --git a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ant/MirrorTaskTest.java b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ant/MirrorTaskTest.java
index 5db1f5cbaa..7ddd801c30 100644
--- a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ant/MirrorTaskTest.java
+++ b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ant/MirrorTaskTest.java
@@ -24,11 +24,11 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
-
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.core.runtime.URIUtil;
@@ -360,7 +360,7 @@ public void testSlicingFollowStrict() {
 		Map<String, String> p = getSliceProperties();
 		p.put("org.eclipse.update.install.features", String.valueOf(true));
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, true, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 
 		try {
@@ -388,7 +388,7 @@ public void testSlicingIncludeNonGreedy() {
 		runAntTask();
 
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, Collections.emptyMap(), true, false, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 		try {
@@ -418,7 +418,7 @@ public void testSlicingIncludeOptionalDependencies() {
 		Map<String, String> p = getSliceProperties();
 		p.put("org.eclipse.update.install.features", String.valueOf(true));
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, false, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 		try {
 			assertIUContentEquals("IUs differ", result, getMetadataRepositoryManager().loadRepository(destinationRepo, null));
@@ -446,7 +446,7 @@ public void testSlicingFilter() {
 
 		Map<String, String> p = getSliceProperties();
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 		try {
 			assertIUContentEquals("IUs differ", result, getMetadataRepositoryManager().loadRepository(destinationRepo, null));
@@ -478,7 +478,7 @@ public void testSlicingPlatformFilter() {
 		Map<String, String> p = getSliceProperties();
 		p.put("org.eclipse.update.install.features", String.valueOf(true));
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 		try {
 			assertIUContentEquals("IUs differ", result, getMetadataRepositoryManager().loadRepository(destinationRepo, null));
@@ -510,7 +510,7 @@ public void testSlicingIncludeFeaturesFalse() {
 
 		Map<String, String> p = getSliceProperties();
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 		try {
 			assertIUContentEquals("IUs differ", result, getMetadataRepositoryManager().loadRepository(destinationRepo, null));
@@ -542,7 +542,7 @@ public void testSlicingMetadataAndArtifactsMirrored() {
 
 		Map<String, String> p = getSliceProperties();
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 
 		assertEquals("Different number of IUs", queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getIUCount(destinationRepo));
 		assertEquals("Different number of ArtifactKeys", getArtifactKeyCount(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getArtifactKeyCount(destinationRepo));
@@ -578,7 +578,7 @@ public void testMirrorSlicedIUtoArtifact() {
 
 		Map<String, String> p = getSliceProperties();
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 
 		assertEquals("Different number of ArtifactKeys", getArtifactKeyCount(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getArtifactKeyCount(destinationRepo));
 		assertArtifactKeyContentEquals("Different ArtifactKeys", result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()), destinationRepo);
@@ -611,7 +611,7 @@ public void testMirrorSlicedMultipleIUsToArtifact() {
 
 		Map<String, String> p = getSliceProperties();
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, true, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu, iu2}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu, iu2), new NullProgressMonitor());
 
 		assertEquals("Different number of ArtifactKeys", getArtifactKeyCount(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())), getArtifactKeyCount(destinationRepo));
 		assertArtifactKeyContentEquals("Different ArtifactKeys", result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()), destinationRepo);
diff --git a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/NegationTesting.java b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/NegationTesting.java
index e12cf22285..3d07f17fe0 100644
--- a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/NegationTesting.java
+++ b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/NegationTesting.java
@@ -18,6 +18,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.List;
 import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.equinox.internal.p2.director.ProfileChangeRequest;
 import org.eclipse.equinox.internal.p2.director.Slicer;
@@ -98,7 +99,7 @@ public void testNot4() {
 
 		// Verify that the slice includes iu3 because the requirement from iu1 is a range including the provided capability of iu3.
 		Slicer slicer = new Slicer(repo, Collections.emptyMap(), false);
-		IQueryable<IInstallableUnit> slice = slicer.slice(new IInstallableUnit[] {iu1}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice = slicer.slice(List.of(iu1), new NullProgressMonitor());
 		assertEquals(3, queryResultSize(slice.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
 
 		//Verify that the resolution succeeds and does not return iu3 since it is excluded by the requirement of iu1
@@ -156,7 +157,7 @@ public void testNot5() {
 
 		//Test the slicer. The slice will not contain iu3 because none of the range of iu1 cause it to be brought in.
 		Slicer slicer = new Slicer(repo, Collections.emptyMap(), false);
-		IQueryable<IInstallableUnit> slice = slicer.slice(new IInstallableUnit[] {iu1}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice = slicer.slice(List.of(iu1), new NullProgressMonitor());
 		assertEquals(0, queryResultSize(slice.query(QueryUtil.createIUQuery("ProviderOf1_1_1"), new NullProgressMonitor())));
 		assertEquals(2, queryResultSize(slice.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
 	}
@@ -188,7 +189,7 @@ public void testNot6() {
 
 		//Test the slicer. The slice will not contain iu3 because none of the range of iu1 cause it to be brought in.
 		Slicer slicer = new Slicer(repo, Collections.emptyMap(), false);
-		IQueryable<IInstallableUnit> slice = slicer.slice(new IInstallableUnit[] {iu1}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice = slicer.slice(List.of(iu1), new NullProgressMonitor());
 		assertEquals(0, queryResultSize(slice.query(QueryUtil.createIUQuery("ProviderOf1_1_1"), new NullProgressMonitor())));
 		assertEquals(2, queryResultSize(slice.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
 
@@ -242,7 +243,7 @@ public void testNot7() {
 
 		// Verify that the slice includes iu3 because the requirement from iu1 is a range including the provided capability of iu3.
 		Slicer slicer = new Slicer(repo, Collections.emptyMap(), false);
-		IQueryable<IInstallableUnit> slice = slicer.slice(new IInstallableUnit[] {iu1}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice = slicer.slice(List.of(iu1), new NullProgressMonitor());
 		assertEquals(3, queryResultSize(slice.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
 
 		//Verify that the resolution succeeds and does not return iu3 since it is excluded by the requirement of iu1
@@ -311,12 +312,12 @@ public void testNot8() {
 
 		// Verify that the slice includes iu3
 		Slicer slicer = new Slicer(repo, Collections.emptyMap(), false);
-		IQueryable<IInstallableUnit> slice = slicer.slice(new IInstallableUnit[] {iu1, iu4}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice = slicer.slice(List.of(iu1, iu4), new NullProgressMonitor());
 		assertEquals(4, queryResultSize(slice.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
 
 		// Verify that the slice includes iu3
 		Slicer slicer2 = new Slicer(repo, Collections.emptyMap(), false);
-		IQueryable<IInstallableUnit> slice2 = slicer2.slice(new IInstallableUnit[] {iu4}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice2 = slicer2.slice(List.of(iu4), new NullProgressMonitor());
 		assertEquals(2, queryResultSize(slice2.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
 
 		//Verify that the resolution succeeds and does not return iu3 since it is excluded by the requirement of iu1
diff --git a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/PermissiveSlicerTest.java b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/PermissiveSlicerTest.java
index 1d9ea29827..d0846562b8 100644
--- a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/PermissiveSlicerTest.java
+++ b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/PermissiveSlicerTest.java
@@ -16,6 +16,7 @@
 import java.io.File;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.equinox.internal.p2.director.PermissiveSlicer;
@@ -44,7 +45,7 @@ public void testSliceRCPOut() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, Collections.emptyMap(), true, false, true, false, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertNotNull(result);
 		queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()));
 		assertEquals(66, queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
@@ -57,7 +58,7 @@ public void testSliceRCPWithOptionalPieces() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, Collections.emptyMap(), false, false, true, false, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertNotNull(result);
 		queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()));
 		assertEquals(64, queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
@@ -68,7 +69,7 @@ public void testSliceRCPWithIgnoringGreed() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, Collections.emptyMap(), false, true, true, false, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertNotNull(result);
 		queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()));
 		assertEquals(64, queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
@@ -83,7 +84,7 @@ public void testSliceRCPWithFilter() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, true, false, false, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertNotNull(result);
 		queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()));
 		assertEquals(0, queryResultSize(result.query(QueryUtil.createIUQuery("org.eclipse.swt.motif.linux.x86"), new NullProgressMonitor())));
@@ -99,7 +100,7 @@ public void testStrictDependency() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, false, false, true, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertNotNull(result);
 		queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()));
 		assertEquals(0, queryResultSize(result.query(QueryUtil.createIUQuery("org.eclipse.ecf"), new NullProgressMonitor())));
@@ -111,7 +112,7 @@ public void testExtractPlatformIndependentPieces() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, Collections.emptyMap(), true, false, false, false, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iu), new NullProgressMonitor());
 		assertNotNull(result);
 		queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor()));
 		assertEquals(32, queryResultSize(result.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor())));
@@ -127,7 +128,7 @@ public void testMetaRequirements() {
 		IInstallableUnit a = createIUWithMetaRequirement("A", DEFAULT_VERSION, true, NO_REQUIRES, metaReq);
 
 		PermissiveSlicer slicer = new PermissiveSlicer(createTestMetdataRepository(new IInstallableUnit[] {a, act1}), Collections.emptyMap(), true, false, false, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {a}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(a), new NullProgressMonitor());
 		assertEquals(1, queryResultSize(result.query(QueryUtil.createIUQuery("Action1"), null)));
 	}
 
@@ -139,7 +140,7 @@ public void testValidateIU() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, false, false, true, false);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.swt.cocoa.macosx"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		assertNull(slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor()));
+		assertNull(slicer.slice(List.of(iu), new NullProgressMonitor()));
 		assertNotOK(slicer.getStatus());
 	}
 
@@ -147,7 +148,7 @@ public void testMissingNecessaryPiece() {
 		IRequirement[] req = createRequiredCapabilities("B", "B", new VersionRange("[0.0.0, 1.0.0]"));
 		IInstallableUnit iuA = createIU("A", DEFAULT_VERSION, null, req, NO_PROVIDES, NO_PROPERTIES, null, NO_TP_DATA, true);
 		PermissiveSlicer slicer = new PermissiveSlicer(createTestMetdataRepository(new IInstallableUnit[] {iuA}), Collections.emptyMap(), true, false, false, false, false);
-		IQueryable<IInstallableUnit> result = slicer.slice(new IInstallableUnit[] {iuA}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> result = slicer.slice(List.of(iuA), new NullProgressMonitor());
 		assertNotNull(result);
 		assertNotOK(slicer.getStatus());
 	}
@@ -160,7 +161,7 @@ public void testExtractOnlyPlatformSpecificForOnePlatform() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, p, true, false, false, false, true);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryResult<IInstallableUnit> resultCollector = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor()).query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor());
+		IQueryResult<IInstallableUnit> resultCollector = slicer.slice(List.of(iu), new NullProgressMonitor()).query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor());
 		assertEquals(3, queryResultSize(resultCollector));
 	}
 
@@ -168,7 +169,8 @@ public void testExtractOnlyPlatformSpecific() {
 		PermissiveSlicer slicer = new PermissiveSlicer(repo, Collections.emptyMap(), true, false, true, false, true);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUQuery("org.eclipse.rcp.feature.group"), new NullProgressMonitor());
 		IInstallableUnit iu = c.iterator().next();
-		IQueryResult<IInstallableUnit> resultCollector = slicer.slice(new IInstallableUnit[] {iu}, new NullProgressMonitor()).query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor());
+		IQueryResult<IInstallableUnit> resultCollector = slicer.slice(List.of(iu), new NullProgressMonitor())
+				.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor());
 		assertEquals(35, queryResultSize(resultCollector));
 	}
 
diff --git a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/SlicerBug365124Test.java b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/SlicerBug365124Test.java
index c8c2c20baa..7e8f9fd7ae 100644
--- a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/SlicerBug365124Test.java
+++ b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/SlicerBug365124Test.java
@@ -54,7 +54,7 @@ private Map<String, String> getProperties() {
 	public void testSlice() {
 		Slicer slicer = new Slicer(getProfile(IProfileRegistry.SELF), getProperties(), true);
 		IQueryResult<IInstallableUnit> c = repo.query(QueryUtil.createIUAnyQuery(), new NullProgressMonitor());
-		slicer.slice(c.toArray(IInstallableUnit.class), new NullProgressMonitor());
+		slicer.slice(c.toUnmodifiableSet(), new NullProgressMonitor());
 		assertNotOK("1.0", slicer.getStatus());
 	}
 
diff --git a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/TychoUsage.java b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/TychoUsage.java
index edcf5fa72d..aed5648bbe 100644
--- a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/TychoUsage.java
+++ b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/planner/TychoUsage.java
@@ -5,6 +5,7 @@
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.NullProgressMonitor;
@@ -72,7 +73,7 @@ public void testTychoUsage() throws ProvisionException, URISyntaxException {
 		context.put("org.eclipse.update.install.features", "true");
 
 		Slicer slicer = new Slicer(repo, context, false);
-		IQueryable<IInstallableUnit> slice = slicer.slice(new IInstallableUnit[] {topLevelIU}, new NullProgressMonitor());
+		IQueryable<IInstallableUnit> slice = slicer.slice(List.of(topLevelIU), new NullProgressMonitor());
 
 		Projector p = new Projector(slice, context, new HashSet<>(), false);
 		p.encode(topLevelIU, new IInstallableUnit[0], new Collector<>(), newRoots, new NullProgressMonitor());
diff --git a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ql/PerformanceTest.java b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ql/PerformanceTest.java
index 734550617f..27911c3cca 100644
--- a/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ql/PerformanceTest.java
+++ b/bundles/org.eclipse.equinox.p2.tests/src/org/eclipse/equinox/p2/tests/ql/PerformanceTest.java
@@ -367,7 +367,7 @@ public void testSlicerPerformance() throws Exception {
 
 			startTime = System.currentTimeMillis();
 			Slicer slicer = new Slicer(new QueryableArray(gatherAvailableInstallableUnits(repo)), env, false);
-			slice = slicer.slice(roots, new NullProgressMonitor());
+			slice = slicer.slice(r.toUnmodifiableSet(), new NullProgressMonitor());
 			sliceTime += (System.currentTimeMillis() - startTime);
 		}
 		// Check the size of the last slice to verify that it's the same as the traverse size
@@ -413,7 +413,7 @@ public void testPermissiveSlicerPerformance() throws Exception {
 
 			startTime = System.currentTimeMillis();
 			Slicer slicer = new PermissiveSlicer(repo, env, true, true, true, false, false);
-			slice = slicer.slice(roots, new NullProgressMonitor());
+			slice = slicer.slice(r.toUnmodifiableSet(), new NullProgressMonitor());
 			sliceTime += (System.currentTimeMillis() - startTime);
 		}
 		// Check the size of the last slice to verify that it's the same as the traverse size