From 3a0dd5d6985f1fcb6bbcae9500706dab2d8e3f22 Mon Sep 17 00:00:00 2001
From: DiegoMarti2 <150871541+DiegoMarti2@users.noreply.github.com>
Date: Wed, 24 Apr 2024 20:48:34 +0200
Subject: [PATCH] baeldung-articles : BAEL-7649 (#16452)

Unit Test for hashCode() in Java.
---
 .../testhashcode/HahCodeUnitTest.java         | 42 +++++++++++++++++++
 .../com/baeldung/testhashcode/MyClass.java    | 15 +++++++
 2 files changed, 57 insertions(+)
 create mode 100644 core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/HahCodeUnitTest.java
 create mode 100644 core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/MyClass.java

diff --git a/core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/HahCodeUnitTest.java b/core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/HahCodeUnitTest.java
new file mode 100644
index 0000000000..6b38d9487e
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/HahCodeUnitTest.java
@@ -0,0 +1,42 @@
+package com.baeldung.testhashcode;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+
+public class HahCodeUnitTest {
+    @Test
+    public void givenObject_whenTestingHashCodeConsistency_thenConsistentHashCodeReturned() {
+        MyClass obj = new MyClass("value");
+        int hashCode1 = obj.hashCode();
+        int hashCode2 = obj.hashCode();
+        assertEquals(hashCode1, hashCode2);
+    }
+
+    @Test
+    public void givenTwoEqualObjects_whenTestingHashCodeEquality_thenEqualHashCodesReturned() {
+        MyClass obj1 = new MyClass("value");
+        MyClass obj2 = new MyClass("value");
+        assertEquals(obj1.hashCode(), obj2.hashCode());
+    }
+
+    @Test
+    public void givenMultipleObjects_whenTestingHashCodeDistribution_thenEvenDistributionOfHashCodes() {
+        List<MyClass> objects = new ArrayList<>();
+        for (int i = 0; i < 1000; i++) {
+            objects.add(new MyClass("value" + i));
+        }
+
+        Set<Integer> hashCodes = new HashSet<>();
+        for (MyClass obj : objects) {
+            hashCodes.add(obj.hashCode());
+        }
+
+        assertEquals(objects.size(), hashCodes.size(), 10);
+    }
+}
\ No newline at end of file
diff --git a/core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/MyClass.java b/core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/MyClass.java
new file mode 100644
index 0000000000..52c42ed68c
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-methods/src/test/java/com/baeldung/testhashcode/MyClass.java
@@ -0,0 +1,15 @@
+package com.baeldung.testhashcode;
+
+public class MyClass {
+    private String value;
+
+    public MyClass(String value) {
+        this.value = value;
+    }
+
+    @Override
+    public int hashCode() {
+        return value != null ? value.hashCode() : 0;
+    }
+
+}