Pre Increment vs Post Increment Java Flaws-CodePudding

public static void insertionSort(int[] array) {
    for (int i = 1; i < array.length; i  ) {
        int key = array[i];
        
        while (i > 0 && key < array[i-1]) {
            array[i--] = array[i-1];
        }
    
        array[i] = key;
    }

I got this piece of code and don't really understand how the array[i--] part works. Based on my understanding, i-- changes the value of i after the statement is ran while --i changed the value of i after expression. However, in this case, array[i--] is not the same as array[i] and put the i-- part under the statement. Can everyone explain? Doesn't this means that array[i--] in this case is the same as array[--i]?

CodePudding user response：

Learn about pre and post increment operator.
Try to avoid such type of statement, because it decreases code readability

    int a=5,b;

    b =   a; //equivalent to: a = a 1; b = a;
    System.out.println(b " - " a); // 6 - 6

    a = 6;
    b = a  ; //equivalent to: b = a; a = a 1
    System.out.println(a " - " b); // 7 6


    int[] arr = {1,2,3,4};

    int i=3;

    while(i!=0){
        System.out.println(arr[i--]); // 4 3 2
// --- equivalent to below two statments: ---
//            System.out.println(arr[i]);
//            i = i-1;
        }

CodePudding user response：

array[i--] = array[i-1];

is same as

array[i] = array[i - 1 - 1];
i = i - 1; // or: i -= 1; or: i--; or: --i;

The post decrement i-- will happen directly after reading the value of i and not after finishing the complete statement.