1.Object类的equals方法（源码）

public boolean equals(Object obj) {
        return (this == obj);//判断如果比较的两个对象是同一个对象，则返回true
    }

2.String类重写Object类的equals方法（源码）

    public boolean equals(Object anObject) {
//判断如果比较的两个对象是同一个对象，则直接返回true
        if (this == anObject) {
            return true;
        }
        if (anObject instanceof String) { //类型判断，是String类才比较
            String anotherString = (String)anObject;//向下转型，需要得到anObject的属性
            int n = value.length;
            if (n == anotherString.value.length) {
                char v1[] = value;
                char v2[] = anotherString.value;
                int i = 0;
                while (n-- != 0) {
                    if (v1[i] != v2[i])
                        return false;
                    i++;
                }
                return true;
            }
        }
        return false;
    }

3.Integer类重写Object类的equals方法（源码）

    public boolean equals(Object obj) {
        if (obj instanceof Integer) { //判断obj是不是Integer类，是才比较
            return value == ((Integer)obj).intValue();//向下转型，如果值相等就返回true
        }
        return false;
    }

4.自写equals方法

自定义Person类（并在Person类中重写Object类的equals方法）：

package oop.demo07;

public class Person {
    private String name;
    private int age;
    private char gender;

    public Person() {
    }

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

    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;
    }

    public char getGender() {
        return gender;
    }

    public void setGender(char gender) {
        this.gender = gender;
    }

    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj instanceof Person) {
            Person p = (Person) obj;
            return this.name.equals(p.name) && this.age == p.age && this.gender == p.gender;
        }
        return false;
    }

}

定义测试类：

package oop.demo07;

public class EqualsTest  {
    public static void main(String[] args) {
        Person person1 = new Person("zs",22,'男');
        Person person2 = new Person("zs",22,'男');
        Person person3 = new Person("lisi",22,'男');

        System.out.println(person1.equals(person2));
        System.out.println(person1.equals(person3));


    }


    }

结果：