BAEL-4925 (#10746)

* BAEL-4925

* BAEL-4925

core-java-modules/core-java-lang-4/src/main/java/com/baeldung/hash/Player.java

@@ -0,0 +1,91 @@
+package com.baeldung.hash;
+
+import java.util.Objects;
+
+public class Player {
+    private String firstName;
+    private String lastName;
+    private String position;
+
+    public Player() {
+
+    }
+
+    public Player(String firstName, String lastName, String position) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        this.position = position;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public String getPosition() {
+        return position;
+    }
+
+    public void setPosition(String position) {
+        this.position = position;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(firstName, lastName, position);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (obj == null) {
+            return false;
+        }
+
+        if (getClass() != obj.getClass()) {
+            return false;
+        }
+
+        Player other = (Player) obj;
+
+        if (firstName == null) {
+            if (other.firstName != null) {
+                return false;
+            }
+        } else if (!firstName.equals(other.firstName)) {
+            return false;
+        }
+
+        if (lastName == null) {
+            if (other.lastName != null) {
+                return false;
+            }
+        } else if (!lastName.equals(other.lastName)) {
+            return false;
+        }
+
+        if (position == null) {
+            if (other.position != null) {
+                return false;
+            }
+        } else if (!position.equals(other.position)) {
+            return false;
+        }
+        return true;
+    }
+
+}

core-java-modules/core-java-lang-4/src/test/java/com/baeldung/hash/HashCodeUnitTest.java

@@ -0,0 +1,67 @@
+package com.baeldung.hash;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+import java.util.Objects;
+
+import org.junit.Test;
+
+public class HashCodeUnitTest {
+
+    @Test
+    public void whenCallingObjectsHashCodeOnIndenticalObjects_thenSameHashCodeReturned() {
+        String stringOne = "test";
+        String stringTwo = "test";
+        int hashCode1 = Objects.hashCode(stringOne);
+        int hashCode2 = Objects.hashCode(stringTwo);
+
+        assertEquals(hashCode1, hashCode2);
+    }
+
+    @Test
+    public void whenCallingObjectsHashCodeOnNullObject_thenZeroReturned() {
+        String nullString = null;
+        int hashCode = Objects.hashCode(nullString);
+        assertEquals(0, hashCode);
+    }
+
+    @Test
+    public void whenCallingObjectHashCodeOnIndenticalObjects_thenSameHashCodeReturned() {
+        Double valueOne = Double.valueOf(1.0012);
+        Double valueTwo = Double.valueOf(1.0012);
+
+        int hashCode1 = valueOne.hashCode();
+        int hashCode2 = valueTwo.hashCode();
+
+        assertEquals(hashCode1, hashCode2);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenCallingObjectHashCodeOnNullObject_theNullPointerExceptionThrown() {
+        Double value = null;
+        value.hashCode();
+    }
+
+    @Test
+    public void whenCallingObjectsHashOnStrings_thenSameHashCodeReturned() {
+        String strOne = "one";
+        String strTwo = "two";
+        String strOne2 = "one";
+        String strTwo2 = "two";
+
+        int hashCode1 = Objects.hash(strOne, strTwo);
+        int hashCode2 = Objects.hash(strOne2, strTwo2);
+
+        assertEquals(hashCode1, hashCode2);
+    }
+
+    @Test
+    public void whenCallingObjectsHashOnSingleString_thenDifferentHashcodeFromObjectsHashCodeCallReturned() {
+        String testString = "test string";
+        int hashCode1 = Objects.hash(testString);
+        int hashCode2 = Objects.hashCode(testString);
+
+        assertNotEquals(hashCode1, hashCode2);
+    }
+}

core-java-modules/core-java-lang-4/src/test/java/com/baeldung/hash/PlayerUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.hash;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+
+public class PlayerUnitTest {
+
+    @Test
+    public void whenCallingHashCodeOnIdenticalValue_thenSameHashCodeReturned() {
+        Player player = new Player("Eduardo", "Rodriguez", "Pitcher");
+        Player indenticalPlayer = new Player("Eduardo", "Rodriguez", "Pitcher");
+
+        int hashCode1 = player.hashCode();
+        int hashCode2 = player.hashCode();
+        int hashCode3 = indenticalPlayer.hashCode();
+
+        assertEquals(hashCode1, hashCode2);
+        assertEquals(hashCode1, hashCode3);
+    }
+
+    @Test
+    public void whenCallingHashCodeAndArraysHashCode_thenSameHashCodeReturned() {
+        Player player = new Player("Bobby", "Dalbec", "First Base");
+        int hashcode1 = player.hashCode();
+        String[] playerInfo = { "Bobby", "Dalbec", "First Base" };
+        int hashcode2 = Arrays.hashCode(playerInfo);
+
+        assertEquals(hashcode1, hashcode2);
+    }
+}