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BAEL 5414 - Java null check why use == instead of .equals() (eugenp#12124)
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‎core-java-modules/core-java-lang-5/README.md‎

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## Core Java Lang (Part 5)
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This module contains articles about core features in the Java language
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## TODO ##

‎core-java-modules/core-java-lang-5/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-java-lang-5</artifactId>
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<version>0.1.0-SNAPSHOT</version>
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<name>core-java-lang-5</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung.core-java-modules</groupId>
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<artifactId>core-java-modules</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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</parent>
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<build>
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<finalName>core-java-lang-5</finalName>
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<resources>
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<resource>
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<directory>src/main/resources</directory>
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<filtering>true</filtering>
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</resource>
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</resources>
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</build>
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</project>

‎core-java-modules/core-java-lang-5/src/test/java/com/baeldung/nullchecks/NullChecksUnitTest.java‎

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package com.baeldung.nullchecks;
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import org.junit.Test;
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import java.util.Objects;
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import static org.junit.jupiter.api.Assertions.*;
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public class NullChecksUnitTest {
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@Test
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public void whenReferenceEqualityOnPrimitives_thenCompareValues() {
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int a = 10;
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int b = 15;
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int c = 10;
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int d = a;
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// different values check
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assertFalse(a == b);
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// same values check
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assertTrue(a == c);
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// same references check
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assertTrue(a == d);
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}
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@Test
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public void whenReferenceEqualityOnObjects_thenCompareReferences() {
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Person a = new Person("Bob", 20);
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Person b = new Person("Mike", 40);
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Person c = new Person("Bob", 20);
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Person d = a;
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Person e = null;
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// different values check
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assertFalse(a == b);
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// same values check
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assertFalse(a == c);
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// same references check
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assertTrue(a == d);
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// same references check - for nulls
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assertTrue(e == null);
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}
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@Test
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public void whenValueEqualityOnPrimitives_thenCompareValues() {
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int a = 10;
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Integer b = a;
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assertTrue(b.equals(10));
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}
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@Test
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public void whenValueEqualityOnObjects_thenCompareValues() {
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Person a = new Person("Bob", 20);
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Person b = new Person("Mike", 40);
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Person c = new Person("Bob", 20);
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Person d = a;
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Person e = null;
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// different values check
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assertFalse(a.equals(b));
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// same values check
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assertTrue(a.equals(c));
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// same references check
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assertTrue(a.equals(d));
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// null checks
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assertFalse(a.equals(e));
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assertThrows(NullPointerException.class, () -> e.equals(a));
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// null checks fixed
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assertFalse(e != null && e.equals(a));
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// using Objects.equals
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assertFalse(Objects.equals(e, a));
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assertTrue(Objects.equals(null, e));
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}
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private class Person {
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private String name;
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private int age;
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public Person(String name, int age) {
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this.name = name;
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this.age = age;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public int getAge() {
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return age;
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}
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public void setAge(int age) {
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this.age = age;
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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Person person = (Person) o;
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return age == person.age && Objects.equals(name, person.name);
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}
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@Override
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public int hashCode() {
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return Objects.hash(name, age);
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}
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}
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}

‎core-java-modules/pom.xml‎

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<module>core-java-lang-2</module>
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<module>core-java-lang-3</module>
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<module>core-java-lang-4</module>
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<module>core-java-lang-5</module>
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<module>core-java-lang-math</module>
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<module>core-java-lang-math-2</module>
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<module>core-java-lang-math-3</module>

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