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class ReturnRef {
  // Internal state, may contain sensitive data
  Hashtable&lt;Integer,String&gt;Hashtable<Integer,String> ht = new Hashtable&lt;Integer,String&gt;Hashtable<Integer,String>(); 
 
  private ReturnRef() {
    ht.put(1, &quot;"123-45-6666&quot;");
  }
 
  public Hashtable&lt;Integer,String&gt;Hashtable<Integer,String> getValues(){ 
    return ht;
  }
 
  public static void main(String[] args) {
    ReturnRef rr = new ReturnRef();
    Hashtable&lt;IntegerHashtable<Integer, String&gt;String> ht1 = rr.getValues(); // Prints sensitive data 123-45-6666
    ht1.remove(1); // Untrusted caller can remove entries
    Hashtable&lt;IntegerHashtable<Integer, String&gt;String> ht2 = rr.getValues(); // Now prints null, original entry is removed
  }	
}

private Hashtable&lt;Integer,String&gt;Hashtable<Integer,String> getValues(){
  return (Hashtable&lt;Integer,String&gt;Hashtable<Integer,String>)ht.clone(); // shallow copy
}

public static void main(String[] args) {
  ReturnRef rr = new ReturnRef();
  Hashtable&lt;Integer,String&gt;Hashtable<Integer,String> ht1 = rr.getValues(); // prints non sensitive data
  ht1.remove(1); // untrusted caller can remove entries only from the copy
  Hashtable&lt;Integer,String&gt;Hashtable<Integer,String> ht2 = rr.getValues(); // prints non sensitive data     
}