.gitignore

@@ -1 +1,2 @@
-/target/
+/target/
+/nbproject/

src/main/java/difflib/text/StringUtils.java

@@ -21,6 +21,7 @@ package difflib.text;
 
 import java.util.LinkedList;
 import java.util.List;
+import static java.util.stream.Collectors.toList;
 
 final class StringUtils {
 
@@ -39,19 +40,15 @@ final class StringUtils {
     }
 
     public static List<String> normalize(List<String> list) {
-        List<String> result = new LinkedList<>();
-        for (String line : list) {
-            result.add(normalize(line));
-        }
-        return result;
+        return list.stream()
+                .map(StringUtils::normalize)
+                .collect(toList());
     }
 
     public static List<String> wrapText(List<String> list, int columnWidth) {
-        List<String> result = new LinkedList<>();
-        for (String line : list) {
-            result.add(wrapText(line, columnWidth));
-        }
-        return result;
+        return list.stream()
+                .map(line -> wrapText(line, columnWidth))
+                .collect(toList());
     }
 
     /**
@@ -62,19 +59,23 @@ final class StringUtils {
      * @return the wrapped text
      */
     public static String wrapText(String line, int columnWidth) {
-        int lenght = line.length();
-        int delimiter = "<br>".length();
+        if (columnWidth <= 0) {
+            throw new IllegalArgumentException("columnWidth may not be less or equal 0");
+        }
+        int length = line.length();
+        int delimiter = "<br/>".length();
         int widthIndex = columnWidth;
 
-        for (int count = 0; lenght > widthIndex; count++) {
-            line = line.subSequence(0, widthIndex + delimiter * count) + "<br>"
-                    + line.substring(widthIndex + delimiter * count);
+        StringBuilder b = new StringBuilder(line);
+
+        for (int count = 0; length > widthIndex; count++) {
+            b.insert(widthIndex + delimiter * count, "<br/>");
             widthIndex += columnWidth;
         }
 
-        return line;
+        return b.toString();
     }
-    
+
     private StringUtils() {
     }
 }

src/test/java/difflib/text/StringUtilsTest.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2017 java-diff-utils.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package difflib.text;
+
+import java.util.Collections;
+import java.util.List;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ *
+ * @author tw
+ */
+public class StringUtilsTest {
+    
+    public StringUtilsTest() {
+    }
+    
+    @BeforeClass
+    public static void setUpClass() {
+    }
+    
+    @AfterClass
+    public static void tearDownClass() {
+    }
+    
+    @Before
+    public void setUp() {
+    }
+    
+    @After
+    public void tearDown() {
+    }
+
+    /**
+     * Test of htmlEntites method, of class StringUtils.
+     */
+    @Test
+    public void testHtmlEntites() {
+        assertEquals("&lt;test&gt;", StringUtils.htmlEntites("<test>"));
+    }
+
+    /**
+     * Test of normalize method, of class StringUtils.
+     */
+    @Test
+    public void testNormalize_String() {
+        assertEquals("    test",StringUtils.normalize("\ttest"));
+    }
+
+    /**
+     * Test of normalize method, of class StringUtils.
+     */
+    @Test
+    public void testNormalize_List() {
+        assertEquals(Collections.singletonList("    test"),StringUtils.normalize(Collections.singletonList("\ttest")));
+    }
+
+    /**
+     * Test of wrapText method, of class StringUtils.
+     */
+    @Test
+    public void testWrapText_String_int() {
+        assertEquals("te<br/>st", StringUtils.wrapText("test", 2));
+        assertEquals("tes<br/>t", StringUtils.wrapText("test", 3));
+        assertEquals("test", StringUtils.wrapText("test", 10));
+    }
+    
+    @Test(expected = IllegalArgumentException.class)
+    public void testWrapText_String_int_zero() {
+        assertEquals("test", StringUtils.wrapText("test", 0));
+    }
+    
+}