这是indexloc提供的服务，不要输入任何密码
Skip to content

BAEL 5414 - Java null check why use == instead of .equals() #12124

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
May 5, 2022
Merged

BAEL 5414 - Java null check why use == instead of .equals() #12124

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions core-java-modules/core-java-lang-5/README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
## Core Java Lang (Part 5)

This module contains articles about core features in the Java language

## TODO ##
27 changes: 27 additions & 0 deletions core-java-modules/core-java-lang-5/pom.xml
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-lang-5</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-lang-5</name>
<packaging>jar</packaging>

<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>

<build>
<finalName>core-java-lang-5</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
</build>

</project>
125 changes: 125 additions & 0 deletions ...va-modules/core-java-lang-5/src/test/java/com/baeldung/nullchecks/NullChecksUnitTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,125 @@
package com.baeldung.nullchecks;

import org.junit.Test;

import java.util.Objects;

import static org.junit.jupiter.api.Assertions.*;

public class NullChecksUnitTest {

@Test
public void whenReferenceEqualityOnPrimitives_thenCompareValues() {
int a = 10;
int b = 15;
int c = 10;
int d = a;

// different values check
assertFalse(a == b);

// same values check
assertTrue(a == c);

// same references check
assertTrue(a == d);
}

@Test
public void whenReferenceEqualityOnObjects_thenCompareReferences() {
Person a = new Person("Bob", 20);
Person b = new Person("Mike", 40);
Person c = new Person("Bob", 20);
Person d = a;
Person e = null;

// different values check
assertFalse(a == b);

// same values check
assertFalse(a == c);

// same references check
assertTrue(a == d);

// same references check - for nulls
assertTrue(e == null);
}

@Test
public void whenValueEqualityOnPrimitives_thenCompareValues() {
int a = 10;
Integer b = a;

assertTrue(b.equals(10));
}

@Test
public void whenValueEqualityOnObjects_thenCompareValues() {
Person a = new Person("Bob", 20);
Person b = new Person("Mike", 40);
Person c = new Person("Bob", 20);
Person d = a;
Person e = null;

// different values check
assertFalse(a.equals(b));

// same values check
assertTrue(a.equals(c));

// same references check
assertTrue(a.equals(d));

// null checks
assertFalse(a.equals(e));
assertThrows(NullPointerException.class, () -> e.equals(a));

// null checks fixed
assertFalse(e != null && e.equals(a));

// using Objects.equals
assertFalse(Objects.equals(e, a));
assertTrue(Objects.equals(null, e));

}

private class Person {
private String name;
private int age;

public Person(String name, int age) {
this.name = name;
this.age = age;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Person person = (Person) o;
return age == person.age && Objects.equals(name, person.name);
}

@Override
public int hashCode() {
return Objects.hash(name, age);
}
}
}
1 change: 1 addition & 0 deletions core-java-modules/pom.xml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@
<module>core-java-lang-2</module>
<module>core-java-lang-3</module>
<module>core-java-lang-4</module>
<module>core-java-lang-5</module>
<module>core-java-lang-math</module>
<module>core-java-lang-math-2</module>
<module>core-java-lang-math-3</module>
Expand Down