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    <p>You can't have the <code>TreeMap</code> itself sort on the values, since that defies the <a href="http://java.sun.com/javase/6/docs/api/java/util/SortedMap.html" rel="noreferrer"><code>SortedMap</code></a> specification:</p> <blockquote> <p>A <code>Map</code> that further provides a <em>total ordering</em> on its <strong>keys</strong>. </p> </blockquote> <p>However, using an external collection, you can always sort <a href="http://java.sun.com/javase/6/docs/api/java/util/Map.html#entrySet%28%29" rel="noreferrer"><code>Map.entrySet()</code></a> however you wish, either by keys, values, or even a combination(!!) of the two.</p> <p>Here's a generic method that returns a <code>SortedSet</code> of <code>Map.Entry</code>, given a <code>Map</code> whose values are <code>Comparable</code>:</p> <pre><code>static &lt;K,V extends Comparable&lt;? super V&gt;&gt; SortedSet&lt;Map.Entry&lt;K,V&gt;&gt; entriesSortedByValues(Map&lt;K,V&gt; map) { SortedSet&lt;Map.Entry&lt;K,V&gt;&gt; sortedEntries = new TreeSet&lt;Map.Entry&lt;K,V&gt;&gt;( new Comparator&lt;Map.Entry&lt;K,V&gt;&gt;() { @Override public int compare(Map.Entry&lt;K,V&gt; e1, Map.Entry&lt;K,V&gt; e2) { int res = e1.getValue().compareTo(e2.getValue()); return res != 0 ? res : 1; } } ); sortedEntries.addAll(map.entrySet()); return sortedEntries; } </code></pre> <p>Now you can do the following:</p> <pre><code> Map&lt;String,Integer&gt; map = new TreeMap&lt;String,Integer&gt;(); map.put("A", 3); map.put("B", 2); map.put("C", 1); System.out.println(map); // prints "{A=3, B=2, C=1}" System.out.println(entriesSortedByValues(map)); // prints "[C=1, B=2, A=3]" </code></pre> <p>Note that funky stuff will happen if you try to modify either the <code>SortedSet</code> itself, or the <code>Map.Entry</code> within, because this is no longer a "view" of the original map like <code>entrySet()</code> is.</p> <p>Generally speaking, the need to sort a map's entries by its values is atypical.</p> <hr> <h3>Note on <code>==</code> for <code>Integer</code></h3> <p>Your original comparator compares <code>Integer</code> using <code>==</code>. This is almost always wrong, since <code>==</code> with <code>Integer</code> operands is a reference equality, not value equality.</p> <pre><code> System.out.println(new Integer(0) == new Integer(0)); // prints "false"!!! </code></pre> <h3>Related questions</h3> <ul> <li><a href="https://stackoverflow.com/questions/1514910/when-comparing-two-integers-in-java-does-auto-unboxing-occur">When comparing two Integers in Java does auto-unboxing occur?</a> (NO!!!)</li> <li><a href="https://stackoverflow.com/questions/2831945/is-it-guaranteed-that-new-integeri-i-in-java">Is it guaranteed that <code>new Integer(i) == i</code> in Java?</a> (YES!!!)</li> </ul>
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    1. CO+1 for unintentional == on Integer.
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    2. COif you add map.put("D", 2); the result is still "[C=1, B=2, A=3]" and not "[C=1, B=2, D=2, A=3]"
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    3. COFix: int res = e2.getValue().compareTo(e1.getValue()); return res != 0 ? res : 1;
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