Cannot invoke iterator on type T[]

Question

I'm trying to iterate over the elements of my data structure within an instance method of the structure. Here is the code for my data structure and its methods:

import java.util.Iterator;

public class DropOutStackArray<T> implements DropOutStack<T>{

    private static final int CAP = 10;
    private int bottom, top, size;
    private T[] cstack;


    public static void main(String[] args){
        //System.out.println(2%10);
        //int[] a = new int[10];
        //System.out.println(a.length);
    }

    private class MyIterator implements Iterator<T>{

        private int curr = 0;

        @Override
        public boolean hasNext() {
            return this.curr != DropOutStackArray.this.size;
        }

        @Override
        public T next() {
            if(hasNext()){
                return cstack[curr++];
            }
            return null;
        }

        public void remove(){
            if(curr == 0)
                return;
            cstack[--curr] = cstack[--size];
            cstack[curr] = null;
        }
    }

    @Override
    public Iterator<T> iterator() {
        // TODO Auto-generated method stub
        return new MyIterator();
    }

    public DropOutStackArray(){
        this.cstack = (T[]) new Object[CAP];
        this.bottom = 0; this.top = 0;
        this.size = 0;

    }

    public DropOutStackArray(final int INCAP){
        this.cstack = (T[]) new Object[INCAP];
        this.bottom = 0; this.top = 0;
        this.size = 0;
    }

    @Override
    public void push(T data) {
        // TODO Auto-generated method stub
        if(this.size == this.cstack.length){
            this.cstack[bottom] = data;
            this.bottom = (this.bottom + 1) % this.cstack.length;
            this.top = (this.top + 1) % this.cstack.length;

        }
        this.cstack[this.top] = data;
        this.top = (this.top + 1) % this.cstack.length;
        this.size++;
    }


    @Override
    public T pop(){
        T popped;
        if(!isEmpty()){
            int length = this.cstack.length;
            this.top = (this.top + length - 1) % length;
            popped = this.cstack[this.top];
            this.cstack[this.top] = null;
            this.size--;
        }else{
            throw new StackEmptyException();
        }
        return popped;
    }   


    @Override
    public T peek() {
        // TODO Auto-generated method stub
        if(isEmpty()){
            throw new StackEmptyException();
        }
        T peeked = this.cstack[this.top-1];
        return peeked;
    }


    @Override
    public int size() {
        return this.size;
    }


    @Override
    public boolean isEmpty() {
        if(this.size == 0){
            return true;
        }
        return false;
    }

    public String toString(){
        Iterator<T> itr = this.cstack.iterator();
    }
}

My issue is in the very last method - toString(). When I try creating itr, I get the error posted in the title. Why can't I call the iterator on cstack?

I assume an array does not provide an iterator. Here's a similar question: http://stackoverflow.com/questions/3912765/iterator-for-array — Kulu Limpa, Oct 05 '14 at 22:43
Unfortunately I can't use any Collections interfaces. I've written my own iterator class and I'm forced to use that. — Jeremy Fisher, Oct 05 '14 at 22:45

score 2 · Accepted Answer · answered Oct 05 '14 at 22:49

2

Both of your methods toString() and iterator() are instance methods within the DropOutStackArray<T> class.

So, you should change the following -

Iterator<T> itr = this.cstack.iterator();

to

Iterator<T> itr = this.iterator();

answered Oct 05 '14 at 22:49

Bhesh Gurung

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Cannot invoke iterator on type T[]

1 Answers1