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    <p>Here's a generic way to do it with any class without having to implement Comparable on the class you're sorting or create a custom comparator. I've found instances where I don't want to override compareTo because it serves a different purpose, you can't for enums anyways, and constantly creating wrapper classes is a pain. You can pass in a function that outputs a Comparable object you'd like to use for sorting purposes.</p> <p>The toComparable function is only called once per element in the list (not so for a custom comparator), so it's especially good if that call is expensive for some class. Null values are handled internally, so it's easier to use than a custom comparator. One call to Java 7's TimSort algorithm is drastically more efficient than doing a bunch of O(log N) inserts to a SortedMap (red-black tree or other balanced tree implementation). And you aren't restricted to any particular class or interface.</p> <p>Real world performance increases are significant in many cases. For example, the performance increase is around 5x as fast as using a comparator when sorting Doubles using toString() on a list of size 100k.</p> <pre><code>import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.List; import java.util.ListIterator; public class GenericLetterSorter { public enum Letter { OMEGA_LETTER("Omega"), GAMMA_LETTER("Gamma"), BETA_LETTER("Beta"), ALPHA_LETTER("Alpha"); private final String description; Letter() { description = toString(); } Letter(String description) { this.description = description; } public String getDescription() { return description; } } public static void main(String[] args) { List&lt;Letter&gt; list = new ArrayList&lt;&gt;(Arrays.asList(Letter.values())); sort(list, new ToComparable&lt;Letter&gt;() { @Override public Comparable toComparable(Letter letter) { // sort based on the letter's description return letter == null ? null : letter.getDescription(); } }); for (Letter letter : list) System.out.println(letter == null ? null : letter.name()); } public interface ToComparable&lt;T, C extends Comparable&lt;? super C&gt;&gt; { C toComparable(T t); } public static &lt;T, C extends Comparable&lt;? super C&gt;&gt; void sort(List&lt;T&gt; list, ToComparable&lt;T, C&gt; function) { class Pair implements Comparable&lt;Pair&gt; { final T original; final C comparable; Pair(T original, C comparable) { this.original = original; this.comparable = comparable; } @Override public int compareTo(Pair other) { return comparable == null &amp;&amp; other.comparable == null ? 0 : comparable == null ? -1 : other.comparable == null ? 1 : comparable.compareTo(other.comparable); } } List&lt;Pair&gt; pairs = new ArrayList&lt;&gt;(list.size()); for (T original : list) pairs.add(new Pair(original, function.toComparable(original))); Collections.sort(pairs); ListIterator&lt;T&gt; iter = list.listIterator(); for (Pair pair : pairs) { iter.next(); iter.set(pair.original); } } } </code></pre>
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    1. POHow do I sort enum members alphabetically in Java?
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