[BAEL-9236] by sgrverma23: Comparing text using java-diff-utils (#18549)

* [BAEL-9236] by sgrverma23: comparing text using java-diff-utils

* fixing package name

* removing util package from module

* refactoring test files

* making method static and refactoring Junits accordingly

---------

Co-authored-by: sverma1-godaddy <[email protected]>

Author: sgrverma23

libraries-5/pom.xml

@@ -219,6 +219,11 @@
             <artifactId>restfb</artifactId>
             <version>${com.restfb.version}</version>
         </dependency>
+        <dependency>
+            <groupId>io.github.java-diff-utils</groupId>
+            <artifactId>java-diff-utils</artifactId>
+            <version>${java-diff-utils.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
@@ -238,6 +243,7 @@
         <github-api.version>1.327</github-api.version>
         <com.restfb.version>2025.6.0</com.restfb.version>
         <objenesis.version>3.4</objenesis.version>
+        <java-diff-utils.version>4.12</java-diff-utils.version>
     </properties>
 
 </project>

libraries-5/src/main/java/com/baeldung/javadiffutils/PatchUtil.java

@@ -0,0 +1,13 @@
+package com.baeldung.javadiffutils;
+
+import com.github.difflib.DiffUtils;
+import com.github.difflib.patch.PatchFailedException;
+
+import java.util.List;
+
+public class PatchUtil {
+    public static List<String> apply(List<String> original, List<String> revised) throws PatchFailedException {
+        var patch = DiffUtils.diff(original, revised);
+        return DiffUtils.patch(original, patch);
+    }
+}

libraries-5/src/main/java/com/baeldung/javadiffutils/SideBySideViewUtil.java

@@ -0,0 +1,21 @@
+package com.baeldung.javadiffutils;
+
+import com.github.difflib.DiffUtils;
+import java.util.List;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class SideBySideViewUtil {
+
+    private static final Logger logger = Logger.getLogger(SideBySideViewUtil.class.getName());
+
+    public static void display(List<String> original, List<String> revised)
+    {
+        var patch = DiffUtils.diff(original, revised);
+        patch.getDeltas().forEach(delta -> {
+        logger.log(Level.INFO,"Change: " + delta.getType());
+        logger.log(Level.INFO,"Original: " + delta.getSource().getLines());
+        logger.log(Level.INFO,"Revised: " + delta.getTarget().getLines());
+        });
+    }
+}

libraries-5/src/main/java/com/baeldung/javadiffutils/TextComparatorUtil.java

@@ -0,0 +1,11 @@
+package com.baeldung.javadiffutils;
+
+import com.github.difflib.DiffUtils;
+import com.github.difflib.patch.Patch;
+import java.util.List;
+
+public class TextComparatorUtil {
+    public static Patch<String> compare(List<String> original, List<String> revised) {
+        return DiffUtils.diff(original, revised);
+    }
+}

libraries-5/src/main/java/com/baeldung/javadiffutils/UnifiedDiffGeneratorUtil.java

@@ -0,0 +1,13 @@
+package com.baeldung.javadiffutils;
+
+import com.github.difflib.DiffUtils;
+import com.github.difflib.UnifiedDiffUtils;
+
+import java.util.List;
+
+public class UnifiedDiffGeneratorUtil {
+    public static List<String> generate(List<String> original, List<String> revised, String fileName) {
+        var patch = DiffUtils.diff(original, revised);
+        return UnifiedDiffUtils.generateUnifiedDiff(fileName, fileName + ".new", original, patch, 3);
+    }
+}

libraries-5/src/test/java/com/baeldung/javadiffutils/PatchUtilTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.javadiffutils;
+
+import com.github.difflib.patch.PatchFailedException;
+import org.junit.Test;
+import java.util.List;
+import static org.junit.Assert.assertEquals;
+
+public class PatchUtilTest {
+    @Test
+    public void givenPatch_whenApplied_thenMatchesRevised() throws PatchFailedException {
+        var original = List.of("alpha", "beta", "gamma");
+        var revised = List.of("alpha", "beta-updated", "gamma");
+
+        var result = PatchUtil.apply(original, revised);
+
+        assertEquals(revised, result);
+    }
+}

libraries-5/src/test/java/com/baeldung/javadiffutils/SideBySideViewUtilTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.javadiffutils;
+
+import org.junit.Test;
+
+import java.util.List;
+
+public class SideBySideViewUtilTest {
+
+    @Test
+    public void givenDifferentLists_whenDisplayCalled_thenNoExceptionThrown() {
+        List<String> original = List.of("line1", "line2", "line3");
+        List<String> revised = List.of("line1", "line2-modified", "line3", "line4");
+
+        SideBySideViewUtil.display(original, revised);
+    }
+
+}

libraries-5/src/test/java/com/baeldung/javadiffutils/TextComparatorUtilTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.javadiffutils;
+
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class TextComparatorUtilTest {
+    @Test
+    public void givenDifferentLines_whenCompared_thenDetectsChanges() {
+        var original = List.of("A", "B", "C");
+        var revised = List.of("A", "B", "D");
+
+        var patch = TextComparatorUtil.compare(original, revised);
+
+        assertEquals(1, patch.getDeltas().size());
+        assertEquals("C", patch.getDeltas().get(0).getSource().getLines().get(0));
+        assertEquals("D", patch.getDeltas().get(0).getTarget().getLines().get(0));
+    }
+}

libraries-5/src/test/java/com/baeldung/javadiffutils/UnifiedDiffGeneratorUtilTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.javadiffutils;
+
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertTrue;
+
+public class UnifiedDiffGeneratorUtilTest {
+    @Test
+    public void givenModifiedText_whenUnifiedDiffGenerated_thenContainsExpectedChanges() {
+        var original = List.of("x", "y", "z");
+        var revised = List.of("x", "y-modified", "z");
+
+        var diff = UnifiedDiffGeneratorUtil.generate(original, revised, "test.txt");
+
+        assertTrue(diff.stream().anyMatch(line -> line.contains("-y")));
+        assertTrue(diff.stream().anyMatch(line -> line.contains("+y-modified")));
+    }
+}