详解Java中==和equals()的区别

int a1 = 10;
int a2 = 10;
System.out.println(a1==a2);  //true

float a3 = 5.0f;
float a4 = 5.0f;
System.out.println(a3==a4);  //true

……

int a1 = 10;
byte b1 = 10;
System.out.println(a1==b1);  //true

char c1 = 'A';
int c2 = 65;
System.out.println(c1 == c2);  //true

int a1 = 10;
double d1 = 10.0d;
System.out.println(a1==d1);  //true

int a1 = 10;
char e1 = 10;
System.out.println(a1==e1);  //true

public class Student {
    public String name;
    public int age;

    public Student(){}

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

Student student1 = new Student("Tom", 18);
Student student2 = new Student("Tom", 18);
System.out.println(student1==student2);  //false

Student student1 = new Student("Tom", 18);
Student student2 = new Student("Tom", 18);
System.out.println(student1.equals(student2));  //false

String str1 = new String("cun");
String str2 = new String("cun");
System.out.println(str1==str2);  //false
System.out.println(str1.equals(str2));  //true

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

@Data
public class Student {
    public String name;
    public int age;

    public Student(){}

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

	/**
     * ==是运算符，equals是方法
     * 1. ==
     *      可以使用在基本数据类型变量和引用数据类型变量中
     *      如果比较的是基本数据类型，就是判断两个保存的数据是否相同，不一定类型相同
     *      如果比较的是引用类型，就是比较两个变量是否代表同一对象实体，也就是是否指向同一地址
     *
     * 2. equals
     *      只能适用于引用数据类型
     *      Object类中equals()和==的作用相同
     *      像String、Data、File、包装类等中的equals都是重写了Object类中的equals()方法，比较的是实体内容是否相同
     */