Generator functions equivalent in Java

Question

I would like to implement an Iterator in Java that behaves somewhat like the following generator function in Python:

def iterator(array):
   for         


        

Answer 1

I wish Java had generator/yield, but since it doesn't using Iterators is probably your best bet.

In this example I stuck with arrays, but in general I would advise using Iterable Collection instead, eg. List. In the example I show how it's pretty easy to get iterators for arrays though:

package example.stackoverflow;

import com.sun.xml.internal.xsom.impl.scd.Iterators;

import java.util.Arrays;
import java.util.Iterator;

public class ArrayGenerator<T> implements Iterable<T> {
    private final T[][][] input;

    public ArrayGenerator(T[][][] input) {
        this.input = input;
    }


    @Override
    public Iterator<T> iterator() {
        return new Iter();
    }

    private class Iter implements Iterator<T> {
        private Iterator<T[][]> x;
        private Iterator<T[]> y;
        private Iterator<T> z;

        {
            x = Arrays.asList(input).iterator();
            y = Iterators.empty();
            z = Iterators.empty();
        }

        @Override
        public boolean hasNext() {
            return z.hasNext() || y.hasNext() || x.hasNext();
        }

        @Override
        public T next() {
            while(! z.hasNext()) {
                while(! y.hasNext()) {
                    y = Arrays.asList(x.next()).iterator();
                }
                z = Arrays.asList(y.next()).iterator();
            }
            return z.next();
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException("remove not supported");
        }
    }

    public static void main(String[] args) {
        for(Integer i :
                new ArrayGenerator<Integer>(
                        new Integer[][][]{
                          {
                            {1, 2, 3},
                            {4, 5}
                          },
                          {
                            {},
                            {6}
                          },
                          {
                          },
                          {
                            {7, 8, 9, 10, 11}
                          }
                        }
                )) {
            System.out.print(i + ", ");
        }
    }
}