I was practicing insertion sort in java, but as soon as I replaced the j+1 from ++j in the inner loop it got stucked over there

Question

When I replaced j+1 with ++j it got stuck over there with an infinite loop neither incrementing nor decrementing public class InsertionSort {

public static void main(String[] args) {
    int[] arr= {5,7,6,4,8,9,3,1,2};
    int n = arr.length;
    for(int i = 1 ; i < n ; i++) {
        int j = i-1;
        int key = arr[i];
        while(j>=0&&key<arr[j]) {
            arr[j+1]=arr[j--]; // ***Working Fine***
        }
        arr[++j]=key;
    }
    for (int i : arr) {
        System.out.print(i+" ");
    }


  } 
 }

Getting stucked in the below code

public class InsertionSort {

public static void main(String[] args) {
    int[] arr= {5,7,6,4,8,9,3,1,2};
    int n = arr.length;
    for(int i = 1 ; i < n ; i++) {
        int j = i-1;
        int key = arr[i];
        while(j>=0&&key<arr[j]) {
            arr[++j]=arr[j--];// ***Stucked***
        }
        arr[++j]=key;
    }
    for (int i : arr) {
        System.out.print(i+" ");
    }
    }

}

Answer 1

This is meant to be stuck infinitely. In the first example of j+1, the value of j is not incremented when you do j+1.

while(j>=0&&key<arr[j]) {
        arr[j+1]=arr[j--]; // value of J is not incremented, it's actually decremented by j--.
    }

In the second example of ++j, there are two operations being performed.

Operation 1:

arr[++j] // This operation increments the value of j

Operation 2:

arr[j--] // This operation decrements the value of j

In the same line, you are incrementing and decrementing the value of j. Hence the value of j is never 0 and it's stuck in an infinite loop. Hope this clarifies the issue.