Java: Increment operation not working inside if block

I am writing a small code for bubble sort using Java as below

package raja.programming.bubblesort;
public class Main {
    public static void main(String[] args) {
	// write your code here
        //int[] intArray = {5, -10, 22, 43, 1, 17};
        int[] intArray = { 20, 35, -15, 7, 55, 1, -22 };
        for ( int unsortedArrayIndex = intArray.length -1 ; unsortedArrayIndex > 0 ; unsortedArrayIndex--){
            for ( int index = 0 ; index < unsortedArrayIndex ; index++){
                System.out.println("index " + intArray[index] + " index+1 : " + intArray[index+1] );
                if ( intArray[index] > intArray[index+1]) {
                    swap(intArray, index, index+1);
                }
            }
        }
        for (int num: intArray) {
            System.out.println(num);
        }
    }
    public static void swap( int[] array, int i, int j) {
        if ( i == j) {
            return ;
        }
        System.out.println("swap index " + array[i] + " index+1 : " + array[j] );
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}

In the line if ( intArray[index] > intArray[index+1]) { I am passing as index+1 then only my code working, if I pass i++ or ++i its not working.

What is the reason behind this behaviour, please help me understand?

Thank you.

When you use index + 1 your code compares the element at the position index and the one at the position index +1 and the loop adds 1 at the end of the instuctions inside the loop

But if you use ++i or i++ your code will do the same thing but the index you used will jump by 2 the incrementation of the for loop and the incrementation you did.

it will not work if you do i++ beacuse this will increment i and return the previous value of i before incrementing so it's like you compare the element to itself

But if you use ++i it will increment the value of i and return the value incremented. But in both ways, in one loop, you increment i twice. If you really want to use either of those you need to remove the for loop and use a while loop and use ++i

i think the reason is. if u are using an index i for example and u increment it inside the loop, u will jump the next iteration. i++ is equals to i = i+1, but i+1 is not equals to i=i+1

You are iterating using index, when you are referring the position in an array using index + 1then the value ofindex` variable is not changed.

But if you use index++ or ++index, then you are incrementing the value of the index variable by 1 in that iteration and you will be skipping one index. Because of the same reason, the output array you are getting is unsorted in this case.