Initial commit

.gitignore

@@ -0,0 +1,2 @@
+build/
+.gradle/

README.md

@@ -0,0 +1,22 @@
+# AP Computer Science A FRQ CheckDigit
+
+
+
+Both the instructions on pages 199-202 and the quick reference guide on page 209 are available at this link: **[https://apcentral.collegeboard.org/pdf/ap-computer-science-a-course-and-exam-description.pdf?course=ap-computer-science-a](https://apcentral.collegeboard.org/pdf/ap-computer-science-a-course-and-exam-description.pdf?course=ap-computer-science-a)** 
+
+Correct solution and scoring guidelines are available at this link:
+
+**[https://apcentral.collegeboard.org/pdf/ap-computer-science-a-2019-ced-scoring-guidelines.pdf?course=ap-computer-science-a](https://apcentral.collegeboard.org/pdf/ap-computer-science-a-2019-ced-scoring-guidelines.pdf?course=ap-computer-science-a)** 
+
+ The correct answer outputs should be as follows.   
+
+```
+Part A
+getCheck(283415) -> 6
+getCheck(2183) -> 2
+```
+```
+Part B
+isValid(1592) -> true => valid combo of 159 and its check digit 2
+isValid(1593) -> false => not a valid combo of number 159 and check digit 3 because the check digit of 159 is 2.
+```

build.gradle

@@ -0,0 +1,18 @@
+plugins {
+	id 'java'
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	testImplementation('org.junit.jupiter:junit-jupiter:5.6.0')
+}
+
+test {
+	useJUnitPlatform()
+	testLogging {
+		events "passed", "skipped", "failed"
+	}
+}

src/main/java/CheckDigit.java

@@ -0,0 +1,45 @@
+public class CheckDigit 
+{   
+  /** Returns the check digit for num, as described in part (a).  
+   *  Precondition: The number of digits in num is between one and    
+   *  six, inclusive.  
+   *          num >= 0  
+   */  
+   public static int getCheck(int num) 
+   {  
+     /* to be implemented in part (a) */
+   }
+
+  /** Returns true if numWithCheckDigit is valid, or false    
+   *  otherwise, as described in part (b). 
+   *  Precondition: The number of digits in numWithCheckDigit   
+   *  is between two and seven, inclusive.
+   *                numWithCheckDigit >= 0     
+   */     
+   public static boolean isValid(int numWithCheckDigit)    
+   {      
+     /* to be implemented in part (b) */    
+   }    
+
+   /** Returns the number of digits in num. */    
+   public static int getNumberOfDigits(int num)    
+   {      
+    if(num < 10)
+      return 1;
+    return 1 + getNumberOfDigits(num/10);    
+   }    
+
+   /** Returns the nthdigit of num.      
+    *  Precondition: n >= 1 and n <= the number of digits in num     
+    */    
+    public static int getDigit(int num, int n)    
+    {      
+      int pos = getNumberOfDigits(num)-n+1;
+      while(pos > 1){
+        num/=10;
+        pos--;
+      }
+      return num%10;
+    }     
+
+}

src/main/java/Main.java

@@ -0,0 +1,7 @@
+public class Main {
+  public static void main(String[] args) {
+    System.out.println(CheckDigit.getCheck(159));
+    System.out.println(CheckDigit.isValid(1592));
+    System.out.println(CheckDigit.isValid(1593));
+  }
+}

src/test/java/Tester.java

@@ -0,0 +1,26 @@
+
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import java.io.*;
+
+public class Tester {
+
+   @Test
+   public void partA () {
+      assertEquals(CheckDigit.getCheck(283415),6);
+      assertEquals(CheckDigit.getCheck(2183),2);
+   }
+   @Test
+   public void partB(){
+      assertEquals(CheckDigit.isValid(1592), true);
+      assertEquals(CheckDigit.isValid(1593),false);
+   }
+
+
+}