Added StringUtil utility class

See jpmml/jpmml-evaluator#105

pmml-model/src/main/java/org/jpmml/model/StringUtil.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2018 Villu Ruusmann
+ */
+package org.jpmml.model;
+
+public class StringUtil {
+
+	private StringUtil(){
+	}
+
+	/**
+	 * <p>
+	 * Trims trailing whitespace from a string value.
+	 * According to the PMML specification,
+	 * the leading whitespace is significant, but the trailing whitespace isn't.
+	 * </p>
+	 *
+	 * @see Character#isWhitespace(char)
+	 */
+	static
+	public String trim(String string){
+		int length = string.length();
+
+		int trimmedLength = length;
+
+		while(trimmedLength > 0){
+			char c = string.charAt(trimmedLength - 1);
+
+			if(!Character.isWhitespace(c)){
+				break;
+			}
+
+			trimmedLength--;
+		}
+
+		if(trimmedLength < length){
+			string = string.substring(0, trimmedLength);
+		}
+
+		return string;
+	}
+}

pmml-model/src/test/java/org/jpmml/model/StringUtilTest.java

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+/*
+ * Copyright (c) 2018 Villu Ruusmann
+ */
+package org.jpmml.model;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+public class StringUtilTest {
+
+	@Test
+	public void trim(){
+		String string = "";
+
+		assertSame(string, StringUtil.trim(string));
+
+		string = "token";
+
+		assertSame(string, StringUtil.trim(string));
+
+		string = "\ttoken";
+
+		assertSame(string, StringUtil.trim(string));
+
+		string = "token\n";
+
+		assertEquals("token", StringUtil.trim(string));
+
+		string = "token\r\n";
+
+		assertEquals("token", StringUtil.trim(string));
+
+		string = "\ttoken\n";
+
+		assertEquals("\ttoken", StringUtil.trim(string));
+
+		string = "\ttoken\r\n";
+
+		assertEquals("\ttoken", StringUtil.trim(string));
+	}
+}