java重写hashcode方法,代码编译测试 - 在线编译器(yxjc123.com)

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                    public class ObjHashCodeExample {

    public static void main(String[] args) {
        Person person = new Person(1,"张三", "湖北");
        Person person2 = new Person(1,"张三", "湖北");
        //这里使用equals重写
        System.out.println(person.hashCode());
        System.out.println(person2.hashCode());

        Person2 person2_1 = new Person2(1,"张三", "湖北");
        Person2 person2_2 = new Person2(1,"张三", "湖北");
        //这里不使用equals重写
        System.out.println(person2_1.hashCode());
        System.out.println(person2_2.hashCode());
    }
}


class Person {
    private Integer id;
    private String name;
    private String address;

    public Person(Integer id, String name, String address) {
        this.id = id;
        this.name = name;
        this.address = address;
    }

    @Override
    public int hashCode(){
        final int prime = 31;
        int result = 1;
        //重写每一个变量的hashcode值
        result = prime * result + ((id == null) ? 0 : id.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((address == null) ? 0 : address.hashCode());

        return result;
    }

    @Override
    public boolean equals(Object o) {
        if(o == this)
            return true;
        if(!(o instanceof Person))
            return false;
        if (o instanceof Person) {
            Person person = (Person)o;
            return person.id.equals(id)
                    && person.name.equals(name)
                    && person.address.equals(address)
                    ;
        }
        return false;
    }

}

class Person2 {
    private Integer id;
    private String name;
    private String address;

    public Person2(Integer id, String name, String address) {
        this.id = id;
        this.name = name;
        this.address = address;
    }


}
                

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