Question

Could someone tell me what the purpose of inner classes are? Also when designing the iterator pattern do we have to use inner classes? Would it be better to use inner classes?

Answer 1

Wikipedia has a good article about the inner class.

You don’t need to use the inner classes for the iterator pattern:

import java.util.*; 
public class BitSetIterator implements Iterator<Boolean> { 
    private final BitSet bitset; 
    private int index;

    public BitSetIterator(BitSet bitset) { 
        this.bitset = bitset; 
    }

    public boolean hasNext() {   
        return index < bitset.length(); 
    } 

    public Boolean next() { 
        if (index >= bitset.length()) { 
            throw new NoSuchElementException(); 
        } 
        boolean b = bitset.get(index++); 
        return new Boolean(b); 
    } 

    public void remove() { 
        throw new UnsupportedOperationException(); 
    }
}