Java BucketSort

Question

I'm sure you probably get this a lot from CompSci students, I tried searching but mine looked a lot different from anything else I could find. Anyway, here is my class, it is supposed to sort an array of integers (then in the future be modified to sort objects, but ints will do for now).

My goal is to make an arrayList which is basically a row of buckets. then each bucket is a linked list. I feel like I'm on the right track, but the compiler doesn't like my last line of code, so I've run out of ideas.

here's an update. this is what I have now, but I still don't think it'll work

public void sorter(){
    int highest_int = 0;

    for(int i=0; i<entries.length; i++){
        if (highest_int < entries[i])
        highest_int = entries[i];
        }

ArrayList<LinkedList<Integer>> row = new ArrayList<LinkedList<Integer>>();  
LinkedList<Integer> column = new LinkedList<Integer>();

    while (highest_int>0){
        row.add(column);
        highest_int--;
    }   

    for(int i=0; i<entries.length; i++){
        int j = entries[i];
        column.add(0, j);
        row.set(j, column);
    }



}

Answer 1

The compiler "doesn't like" your code because the add() method of LinkedList doesn't return anything (has void return type). Therefore it cannot be used as an argument to the set() method. Basically, add() modified the object that it is called on, but doesn't return that object as a value.

The simplest change I can suggest that I think will make your code compile would be:

for(int i=0; i<entries.length; i++){
    int j = entries[i];
    column.add(0, j);
    row.set(j, column);
}

Beyond that, it's not clear to me what you are actually trying to accomplish here. I don't see anything that looks like a sort at all.

Answer 2

The compile problem is that column.add() returns void.

A bigger problem is that the same LinkedList is used for each bucket. You need to create a new LinkedList in each iteration of one of the for loops.