blocks|key|240208|text|为什么你认为这种方法不会被优化呢？相反的顺序Comparator将简单地翻转来自实际Comparator的输出符号(或插入的Comparable对象上的compareTo输出)，因此我可以想象它非常快。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|240209|另一个建议是:与其更改存储元素的顺序，不如使用descendingIterator()方法按降序遍历元素。|240210|entityMap^0|M|A|16|A|1Q|A|24|9|0|N|K|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|I|$]]

Why do you think this approach won't be optimized? The reverse order <code>Comparator</code> is simply going to be flipping the sign of the output from the actual <code>Comparator</code> (or output from <code>compareTo</code> on the <code>Comparable</code> objects being inserted) and I would therefore imagine it is very fast.

An alternative suggestion: Rather than change the order you store the elements in you could iterate over them in descending order using the <code>descendingIterator()</code> method.

blocks|key|526283|text|TreeSet::descendingSet|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|526284|在Java6和更高版本中，TreeSet上有一个名为descendingSet()的方法，用于生成NavigableSet接口对象。|526285|526286|+public+NavigableSet+descendingSet()|blockquote|526287|526288|降序集由此集支持，因此对集合的更改反映在降序集中，反之亦然。如果在任一集合上的迭代正在进行中(除非通过迭代器自己的移除操作)，则迭代的结果是未定义的。|526289|返回的集合的排序等价于|526290|比较器(Collections.reverseOrder)。表达式s.descendingSet().descendingSet()返回一个与s本质等价的视图。|526291|接口中由:+descendingSet指定的NavigableSet返回:自:+1.6以来的该集合的反向顺序视图|526292|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/TreeSet.html|1|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/TreeSet.html#descendingSet()|2|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/NavigableSet.html^0|0|M|0|D|7|Q|F|1D|C|D|7|0|Q|F|1|1D|C|2|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@$9|1G|A|1H|1|1I]|$9|1J|A|1K|1|1L]|$9|1M|A|1N|1|1O]]|E|$]]|$1|H|3|-4|5|6|7|1P|8|@]|D|@]|E|$]]|$1|I|3|J|5|K|7|1Q|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|1R|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|1S|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1T|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1U|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1V|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]]|V|$W|$5|X|Y|Z|E|$10|11]]|12|$5|X|Y|Z|E|$10|13]]|14|$5|X|Y|Z|E|$10|15]]]]

<h1><code>TreeSet::descendingSet</code></h1>

In Java 6 and later, there is a method on <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/TreeSet.html" rel="nofollow noreferrer"><code>TreeSet</code></a> called <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/TreeSet.html#descendingSet()" rel="nofollow noreferrer"><code>descendingSet()</code></a> producing a <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/NavigableSet.html" rel="nofollow noreferrer"><code>NavigableSet</code></a> interface object.

<blockquote>
 public NavigableSet descendingSet()
 
 The descending set is backed by this
 set, so changes to the set are
 reflected in the descending set, and
 vice-versa. If either set is modified
 while an iteration over either set is
 in progress (except through the
 iterator's own remove operation), the
 results of the iteration are
 undefined.

<pre><code> The returned set has an ordering equivalent to
</code></pre>
 
 Collections.reverseOrder(comparator()).
 The expression
 s.descendingSet().descendingSet()
 returns a view of s essentially
 equivalent to s.

<pre><code> Specified by:
 descendingSet in interface NavigableSet&lt;E&gt;

 Returns:
 a reverse order view of this set
 Since:
 1.6
</code></pre>
</blockquote>

blocks|key|558814|text|TreeSet<Integer>+treeSetObj+=+new+TreeSet<Integer>(new+Comparator<Integer>()
++{
++public+int+compare(Integer+i1,Integer+i2)
++++++++{
++++++++return+i2.compareTo(i1);
++++++++}
++});|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|558815|有必要翻转结果。但我想这是--.你真的需要这个吗？|unstyled|offset|length|style|BOLD|558816|entityMap^0|0|D|2|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>TreeSet&lt;Integer&gt; treeSetObj = new TreeSet&lt;Integer&gt;(new Comparator&lt;Integer&gt;()
 {
 public int compare(Integer i1,Integer i2)
 {
 return i2.compareTo(i1);
 }
 });
</code></pre>

there is need to flip the result. But I guess this is just a <a href="https://softwareengineering.stackexchange.com/q/99445/34735">micro-optimization</a>... Do you really need this ?

blocks|key|235045|text|使用descendingSet方法可以反转类中现有的treeSet|type|unstyled|depth|inlineStyleRanges|entityRanges|data|235046|import+java.util.TreeSet;+
++
public+class+TreeSetDescending+{+
++
++++public+static+void+main(String[]+args)+
++++{+
++++++++//+Declare+a+treeset+
++++++++TreeSet<Object>+ints+=+new+TreeSet<Object>();+
++++++++ints.add(2);+
++++++++ints.add(20);+
++++++++ints.add(10);+
++++++++ints.add(5);+
++++++++ints.add(7);+
++++++++ints.add(3);+
++
++++++++//+Initialize+treeset+with+predefined+set+in+reverse+order+
++++++++//+using+descendingSet()+
++++++++TreeSet<Object>+intsReverse+=+(TreeSet<Object>)ints.descendingSet();+
++
++++++++//+Print+the+set+
++++++++System.out.println("Without+descendingSet():+"+%2B+ints);+
++++++++System.out.println("With+descendingSet():+"+%2B+intsReverse);+
++++}+
}+|code-block|syntax|javascript|235047|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Using descendingSet method you can reverse existing treeSet in the class
<pre><code>import java.util.TreeSet; 
 
public class TreeSetDescending { 
 
 public static void main(String[] args) 
 { 
 // Declare a treeset 
 TreeSet&lt;Object&gt; ints = new TreeSet&lt;Object&gt;(); 
 ints.add(2); 
 ints.add(20); 
 ints.add(10); 
 ints.add(5); 
 ints.add(7); 
 ints.add(3); 
 
 // Initialize treeset with predefined set in reverse order 
 // using descendingSet() 
 TreeSet&lt;Object&gt; intsReverse = (TreeSet&lt;Object&gt;)ints.descendingSet(); 
 
 // Print the set 
 System.out.println(&quot;Without descendingSet(): &quot; + ints); 
 System.out.println(&quot;With descendingSet(): &quot; + intsReverse); 
 } 
} 
</code></pre>

blocks|key|558847|text|反向compare|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|558848|您可以在compare方法中反转Comparator中两个参数的顺序。|558849|TreeSet+t+=+new+TreeSet(new+MyComparator());
++{
class+MyComparator+implements+Comparator
{
++public+int+compare(Integer+i1,Integer+i2)
++++++++{
+++++++++Integer+I1=(Integer)i1;
+++++++++Integer+I2=(Integer)i2;
+++++++++return+I2.compareTo(I1);++//+return+-I1compareTo(I2);
++++++++}
}
++}|code-block|syntax|javascript|558850|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Comparator.html#compare(T,T)|1|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Comparator.html^0|2|7|0|4|7|G|A|4|7|0|G|A|1|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]|$9|17|A|18|1|19]]|E|$]]|$1|H|3|I|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]|U|$5|P|Q|R|E|$S|V]]]]

<h1>Reverse <code>compare</code></h1>

You can reverse the order of the two arguments in the <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Comparator.html#compare(T,T)" rel="nofollow noreferrer"><code>compare</code></a> method of your <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Comparator.html" rel="nofollow noreferrer"><code>Comparator</code></a>. 

<pre><code>TreeSet t = new TreeSet(new MyComparator());
 {
class MyComparator implements Comparator
{
 public int compare(Integer i1,Integer i2)
 {
 Integer I1=(Integer)i1;
 Integer I2=(Integer)i2;
 return I2.compareTo(I1); // return -I1compareTo(I2);
 }
}
 }
</code></pre>

Here is the piece of code that I have used for Java 5.0
<pre><code>TreeSet&lt;Integer&gt; treeSetObj = new TreeSet&lt;Integer&gt;( Collections.reverseOrder() ) ;
</code></pre>
<code>Collections.reverseOrder()</code> is used to obtain a comparator in order to reverse the way the elements are stored and iterated.
Is there a more optimized way of doing it?

Treeset to order elements in descending order

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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下面是我为Java5.0使用的代码TreeSet<Integer> treeSetObj = new TreeSet<Integer>( Collections.reverseOrder() ) ;Collections.reverseOrder()用于获得一个比较器，以逆转存储和迭代元素的方式。有没有一种更优化的方法来做这件事？

问按降序排列元素的树集
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回答 5

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