Sorting an integer array in java, using selection sort. Cannot find my error

Question

I'm trying to learn code by making 'easy' exercises. I am trying to make a search algorithm using selection sort. When I follow the code inside my head it makes perfect sense, but when I run it, it does not order anything. For the array I am using an integer only array, it consist of random numbers and is of random length.

int currentMin;
    int currentMinIndex = 0;
    int temp;
    for(int i=0;i<array.length-1;i++){
        currentMin = array[i]; 
        for(int j=i+1;j<array.length-1;j++){
            if(array[j]<currentMin){
                currentMinIndex = j; 
                currentMin = array[j];
            }
        }
        temp = array[currentMinIndex]; //I am aware this could be currentMin 
        array[currentMinIndex] = array[i];
        array[i] = temp;
    }

I hope someone will spot my mistake and tell me. (If you have other 'easy' exercises I could do, creativity is appreciated, however this post must stay on topic)

Edit: I just noticed that in some weird way when the array is of large length it sorts but the last one. (array length vary because they are random)

Answer 1

You need to update currentMinIndex to i when you set currentMin, and your inner loop should be to array.length.

currentMin = array[i]; 
currentMinIndex = i;
for(int j=i+1;j<array.length;j++){

You could further simplify this by moving your declarations into the loop and removing temp (as you have currentMin) like

for (int i = 0; i < array.length - 1; i++) {
    int currentMin = array[i];
    int currentMinIndex = i;
    for (int j = i + 1; j < array.length; j++) {
        if (array[j] < currentMin) {
            currentMinIndex = j;
            currentMin = array[j];
        }
    }
    array[currentMinIndex] = array[i];
    array[i] = currentMin;
}