title: Update HashMap values of type HashSet<Integer>
body: <p>I have trouble updating the HashMap values of Set type. After initializing the HashMap with key-values pair, I want to insert a new value to the the existing value Set, and the new value is to be incremented for each insert. My code is following:</p>
  
  <pre><code>    public static void main(String[] args)
      {
          String[] mapKeys = new String[]{"hello", "world", "america"};
          Map&lt;String, Set&lt;Integer&gt;&gt; hashMap1 = new HashMap&lt;String, Set&lt;Integer&gt;&gt;();
          Set&lt;Integer&gt; values = new HashSet&lt;Integer&gt;();
  
          for (int i = 0; i &lt; 10; i++)  // initialize the values to a set of integers[1 through 9]
          {
              values.add(i);
          }
  
          for (String key : mapKeys)
          {
              hashMap1.put(key, values);
          }
  
          StdOut.println("hashMap1 is: " + hashMap1.toString());
  
          int newValues = 100; // insert this newValues (incremented at each insert) to each value
          Set&lt;Integer&gt; valuesCopy;
  
          for (String key : mapKeys)
          {
              if (hashMap1.containsKey(key))
              {
                  valuesCopy = hashMap1.get(key); // first, copy out the existing values
  
                  valuesCopy.add(newValues++); // insert the newValues to the value Set
                  hashMap1.remove(key);// remove the existing entries
                  hashMap1.put(key, valuesCopy); // insert the key-value pairs
  
              }
          }
  
          StdOut.println("the updated hashMap1 is: " + hashMap1.toString());
  
  
      }
  </code></pre>
  
  <p>When executing the code, each HashMap key is associated with the same set of Integers:
  [102, 0, 1, 2, 100, 3, 101, 4, 5, 6, 7, 8, 9], however, what I really want is insert only one number to each set, this is what I want: [0, 1, 2, 100, 3, 4, 5, 6, 7, 8, 9]</p>
  
  <p>I need help understanding this: why all the new inserted values are the same? how to make it work as I wish? thanks for help</p>