From 0323a8168c7ecf9f0991c5c0116272ba95734be3 Mon Sep 17 00:00:00 2001
From: Kai Yuan <kent.yuan@Gmail.com>
Date: Wed, 13 Dec 2023 04:38:31 +0100
Subject: [PATCH] [sum-intarray-recursion] two recursion approaches to summing
 int-array (#15385)

---
 core-java-modules/core-java-lang-6/pom.xml    | 16 +++++
 .../RecursivelySumIntArrayUnitTest.java       | 38 ++++++++++++
 .../SumArrayBenchmark.java                    | 61 +++++++++++++++++++
 3 files changed, 115 insertions(+)
 create mode 100644 core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/RecursivelySumIntArrayUnitTest.java
 create mode 100644 core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/SumArrayBenchmark.java

diff --git a/core-java-modules/core-java-lang-6/pom.xml b/core-java-modules/core-java-lang-6/pom.xml
index 54035c1eb0..a47ed459f6 100644
--- a/core-java-modules/core-java-lang-6/pom.xml
+++ b/core-java-modules/core-java-lang-6/pom.xml
@@ -23,6 +23,16 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>
@@ -39,6 +49,11 @@
                             <artifactId>mapstruct-processor</artifactId>
                             <version>${mapstruct.version}</version>
                         </path>
+                        <path>
+                            <groupId>org.openjdk.jmh</groupId>
+                            <artifactId>jmh-generator-annprocess</artifactId>
+                            <version>${jmh.version}</version>
+                        </path>
                     </annotationProcessorPaths>
                 </configuration>
             </plugin>
@@ -50,6 +65,7 @@
         <maven.compiler.target>17</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <mapstruct.version>1.6.0.Beta1</mapstruct.version>
+        <jmh.version>1.37</jmh.version>
     </properties>
 
 </project>
\ No newline at end of file
diff --git a/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/RecursivelySumIntArrayUnitTest.java b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/RecursivelySumIntArrayUnitTest.java
new file mode 100644
index 0000000000..fc61a806e1
--- /dev/null
+++ b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/RecursivelySumIntArrayUnitTest.java
@@ -0,0 +1,38 @@
+package com.baeldung.recursivelysumintarray;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class RecursivelySumIntArrayUnitTest {
+
+    private static final int[] INT_ARRAY = { 1, 2, 3, 4, 5 };
+
+    static int sumIntArray1(int[] array) {
+        if (array.length == 1) {
+            return array[0];
+        } else {
+            return array[0] + sumIntArray1(Arrays.copyOfRange(array, 1, array.length));
+        }
+    }
+
+    static int sumIntArray2(int[] array, int index) {
+        if (index == 0) {
+            return array[index];
+        } else {
+            return array[index] + sumIntArray2(array, index - 1);
+        }
+    }
+
+    @Test
+    void whenUsingSumIntArray1_thenGetExpectedResult() {
+        assertEquals(15, sumIntArray1(INT_ARRAY));
+    }
+
+    @Test
+    void whenUsingSumIntArray2_thenGetExpectedResult() {
+        assertEquals(15, sumIntArray2(INT_ARRAY, INT_ARRAY.length - 1));
+    }
+}
\ No newline at end of file
diff --git a/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/SumArrayBenchmark.java b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/SumArrayBenchmark.java
new file mode 100644
index 0000000000..7d6a612a8d
--- /dev/null
+++ b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/SumArrayBenchmark.java
@@ -0,0 +1,61 @@
+package com.baeldung.recursivelysumintarray;
+
+import static com.baeldung.recursivelysumintarray.RecursivelySumIntArrayUnitTest.sumIntArray1;
+import static com.baeldung.recursivelysumintarray.RecursivelySumIntArrayUnitTest.sumIntArray2;
+
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@BenchmarkMode(Mode.AverageTime)
+@State(Scope.Thread)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 2)
+@Fork(1)
+@Measurement(iterations = 5)
+public class SumArrayBenchmark {
+
+    public static void main(String[] args) throws Exception {
+        Options options = new OptionsBuilder().include(SumArrayBenchmark.class.getSimpleName())
+          .build();
+        new Runner(options).run();
+    }
+
+    @Param({ "10", "10000" })
+    public int size;
+    int[] array;
+
+    @Setup
+    public void setup() {
+        var r = new Random();
+        array = new int[size];
+
+        for (int i = 0; i < size; i++) {
+            array[i] = r.nextInt();
+        }
+    }
+
+    @Benchmark
+    public int withArrayCopy() {
+        return sumIntArray1(array);
+    }
+
+    @Benchmark
+    public int withoutArrayCopy() {
+        return sumIntArray2(array, array.length - 1);
+    }
+}
\ No newline at end of file