递增和递减更改对象值

Question

任何人都可以告诉我输出变化的原因.

public class Demo {
  public void demo()
  {
        Integer y = 567;
        Integer x = y;
        System.out.println(x + " " + y);
        System.out.println(y == x);
        y++;
        System.out.println(x + " " + y);
        System.out.println(y == x);
        y--;
        System.out.println(x + " " + y);
        System.out.println(y == x);
  }
  public static void main(String args[])
  {
        Demo obj = new Demo();
        obj.demo();
  }
}

输出:

567 567

true

567 568

false

567 567

False

这就是为什么我得到最后的错误.

Answer 1

您正在使用Integer哪个是不可变对象.

基本上你的代码是

y = new Integer(y.intValue() + 1);

和

y = new Integer(y.intValue() - 1);

因此,您要创建两个与前一个对象不同的新Integer对象(==).

此行为在Java中称为自动装箱.

Answer 2

    Integer y = 567; // y=567
    Integer x = y;   // x is equal to y object
    System.out.println(x + " " + y); // out put x and y so obviously x and y are 567
    System.out.println(y == x); // here x and y are in same reference. so this x==y is true and out put is true. 
    y++; // increment y by 1. then y=568
    System.out.println(x + " " + y); // now x= 567 and y= 568
    System.out.println(y == x);// now x not equals to y then false will print
    y--; // again decrement y value
    System.out.println(x + " " + y); // again x and y are same 567
    System.out.println(y == x);// here y.value == x.value but x and y object wise not equal since object x and y are referring deference points