java - How to write HashMap iterator? -

when use iterator = densebagmap.keyset().iterator(), return key once though if contains more once. want able return element let's if 'a' occurs 3 times. next method should able return "a" 3 times not sure how can that. sort of slow in helpful if can show me iterator actual code. hasnext() , next() method required iterator.

public class densebag<t> extends abstractcollection<t> {  private map<t, integer> densebagmap; private int size;  // total number of elements in bag /**  * initialize new, empty densebag  */ public densebag() {     densebagmap = new hashmap<t, integer>();  };     public boolean equals(object o) {     if (o == this) {         return true;     }     if (!(o instanceof densebag)) {         return false;     }     densebag<t> dense = (densebag<t>) o;     return size == dense.size;  }     public int hashcode() {     return this.densebagmap.hashcode();  }     //i not sure how write iterator method this.     public iterator<t> iterator() {     return new iterator<t>() {    public boolean hasnext(){  }    public t next(){  } 

a keyset is, definition, set , therefore contains only 1 entry each key. if wish store entries added under each key should use apache multimap.