What is the problems about java number++?

Question

i have tried this ,found the questions

public class Baz {
    public static void main(String[] args) {
        int num = 5;
        for(int i=0 ;i < 4 ; i++) {
          num = num++;
        }
       System.out.println("Value is :" + num);
    }
}

the result print Values is 5, What happen ?

Answer 1

num = num++;

is the same as

num = num;

because the numerical value of the expression num++ is the value of num before it is incremented; so although num++ has the side-effect of incrementing num, it is immediately reverted by the assignment,

As such, the value of num is left unchanged.

Answer 2

num = num++;   // don't do this

num++ increments the variable, but it first evaluates to the current value, which is then assigned to the variable by num =. The incremented value is just discarded.

In other languages (such as C), this is even undefined behaviour.

Answer 3

num++ is the same as num = num +1

So you should just do as follows:

public class Baz {
    public static void main(String[] args) {
        int num = 5;
    for(int i=0 ;i < 4 ; i++) {
       num++;
    }
   System.out.println("Value is :" + num);
}

}

Answer 4

The line num = num++ makes no sense. num++ is equal to num = num + 1

So you have to change your code into:

public class Baz {
    public static void main(String[] args) {
        int num = 5;
        for(int i=0 ;i < 4 ; i++) {
          num++;
        }
       System.out.println("Value is :" + num);
    }
}