Why this iterator is not working in foreach loop?

Question

I am trying to create my own iterator and use this inside a foreach loop. But getting an error that Object can't be Converted from Object to Integer. Purpose of this code to understand iterator interface.

package com.java.collections;

import java.util.Iterator;

public class Counter implements Iterable {

    int count;

    Counter(int count){
        this.count = count;
    }

    @Override
    public Iterator iterator() {
        // TODO Auto-generated method stub
        return new Iterator<Integer>() {
        private int i = 0;
        @Override
        public boolean hasNext() {
            // TODO Auto-generated method stub

            return i < count;
        }

        @Override
        public Integer next() {
            // TODO Auto-generated method stub
            i++;
            return i;
        }

        @Override
        public void remove() {
            // TODO Auto-generated method stub

        }
    };

    }
}

package com.java.collections;

public class TestCounter {

    public static void main(String[] args) {
        new TestCounter().test();
    }

    void test() {
        for(Integer i : new Counter(5))
        {

        }
    }
}

Jeff Storey · Accepted Answer · 2014-07-24 03:36:41Z

2

You have to use a generic type with iterable (Integer in your case)

public class Counter implements Iterable<Integer> {
...
}

answered Jul 24, 2014 at 3:36

Jeff Storey

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3 Comments

anirban Over a year ago

did that, got error as "Type mismatch: cannot convert from element type Iterable to Integer"

0-4930-42390eo23o2e0-23oe0-23o Over a year ago

You are most likely trying to return the Iterator instead of the Integer in your next() method.

anirban Over a year ago

Yes Jeff, sorry I typed public class Counter implements Iterable<Iterable> in a hurry. Changed that back to Integer. And it worked. Thanks

Thorn · Accepted Answer · 2014-07-24 03:40:47Z

2

The Iterable interface can user generics and since your counter is an integer, you should specify this:

 public class Counter implements Iterable<Integer> {
    //other methods and code omitted

    public Iterator<Integer> iterator() {
        //same code as in posted question
    }
 }

answered Jul 24, 2014 at 3:40

Thorn

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Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

for each requires only array or Iterable

Take a look The enhanced for statement

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Jul 24, 2014 at 3:38

newuser

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