Java實現冒泡算法

int[] arr = {11,7,2,5,9,21};
int size = arr.length;
for(int i = 0 ; i < size ; i++){
    for(int j = size-1 ; j > i ; j--){
        int leftNum = arr[i];
        int rightNum = arr[j];
        if(leftNum > rightNum){
            arr[i] = rightNum;
            arr[j] = leftNum;
        }
    }
}