Examples for 'Finding the difference between two strings in Java' (#7625)

* initial commit

* Reformatting and addressing review comments

* Examples for 'Finding the difference between two strings in Java'

* Removing evaluation article code

* Adding benchmarks

* Removing performance tests from unit test class

* upgrading diff-match-patch version

* making benchmark methods return a value

* Moving code to java-strings-3

* Moving stuff around

* New unit test format

java-strings-3/pom.xml

@@ -68,6 +68,12 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.bitbucket.cowwoc</groupId>
+            <artifactId>diff-match-patch</artifactId>
+            <version>1.2</version>
+            <scope>test</scope>
+        </dependency>
 
         <!-- Added for password generation -->
         <dependency>

java-strings-3/src/test/java/com/baeldung/stringdiff/StringDiffBenchmarkUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.stringdiff;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang3.RandomStringUtils;
+import org.apache.commons.lang3.StringUtils;
+import org.bitbucket.cowwoc.diffmatchpatch.DiffMatchPatch;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@State(Scope.Benchmark)
+public class StringDiffBenchmarkUnitTest {
+
+    private DiffMatchPatch diffMatchPatch = new DiffMatchPatch();
+
+    private List<String> inputs = randomizeInputs(10000);
+
+    public static void main(String[] args) throws RunnerException {
+        Options opts = new OptionsBuilder().include(".*")
+            .warmupIterations(1)
+            .measurementIterations(50)
+            .jvmArgs("-Xms2g", "-Xmx2g")
+            .shouldDoGC(true)
+            .forks(1)
+            .build();
+
+        new Runner(opts).run();
+    }
+
+    @Benchmark
+    public int diffMatchPatch() {
+        for (int i = 0; i < inputs.size() - 1; i++) {
+            diffMatchPatch.diffMain(inputs.get(i), inputs.get(i + 1), false);
+        }
+        return inputs.size();
+    }
+
+    @Benchmark
+    public int stringUtils() {
+        for (int i = 0; i < inputs.size() - 1; i++) {
+            StringUtils.difference(inputs.get(i), inputs.get(i + 1));
+        }
+        return inputs.size();
+    }
+
+    /**
+     * Creates a list of a given size, containing 30 character long strings,
+     * each starting with a static prefix of 10 characters and followed by
+     * a random 20 character suffix
+     *
+     * @return a {@link List} of randomised strings
+     */
+    private List<String> randomizeInputs(int size) {
+        String staticPart = "ABCDEF1234";
+        List<String> inputs = new ArrayList<>();
+        for (int i = 0; i < size; i++) {
+            inputs.add(staticPart + RandomStringUtils.randomAlphabetic(20));
+        }
+        return inputs;
+    }
+}

java-strings-3/src/test/java/com/baeldung/stringdiff/StringDiffUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.stringdiff;
+
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+import org.apache.commons.lang3.StringUtils;
+import org.bitbucket.cowwoc.diffmatchpatch.DiffMatchPatch;
+import org.bitbucket.cowwoc.diffmatchpatch.DiffMatchPatch.Operation;
+import org.junit.Test;
+
+public class StringDiffUnitTest {
+
+    private DiffMatchPatch diffMatchPatch = new DiffMatchPatch();
+
+    // Test samples
+    private final String text1 = "ABCDELMN";
+    private final String text2 = "ABCFGLMN";
+
+    @Test
+    public void givenTwoStrings_whenDiffMatchPatch_thenReturnCorrectDiff() {
+        assertThat(diffMatchPatch.diffMain(text1, text2, false), containsInAnyOrder(
+            new DiffMatchPatch.Diff(Operation.EQUAL, "ABC"),
+            new DiffMatchPatch.Diff(Operation.DELETE, "DE"),
+            new DiffMatchPatch.Diff(Operation.INSERT, "FG"),
+            new DiffMatchPatch.Diff(Operation.EQUAL, "LMN")));
+        assertThat(diffMatchPatch.diffMain(text2, text1, false), containsInAnyOrder(
+            new DiffMatchPatch.Diff(Operation.EQUAL, "ABC"),
+            new DiffMatchPatch.Diff(Operation.INSERT, "DE"),
+            new DiffMatchPatch.Diff(Operation.DELETE, "FG"),
+            new DiffMatchPatch.Diff(Operation.EQUAL, "LMN")));
+    }
+
+    @Test
+    public void givenTwoStrings_whenStringUtilsDifference_thenReturnCorrectDiff() {
+        assertThat(StringUtils.difference(text1, text2), is("FGLMN"));
+        assertThat(StringUtils.difference(text2, text1), is("DELMN"));
+    }
+}