Java ConcurrentSkipListSet descendingSet()方法

java.util.concurrent.ConcurrentSkipListSet 的 descendingSet() 方法是Java中的一个内置函数，它返回这个集合中包含的元素的反向顺序视图。降序集合是由这个集合支持的，所以这个集合的变化会反映在降序集合中，反之亦然。

语法

ConcurrentSkipListSet.descendingSet()

返回值： 该函数返回一个NavigableSet，它是这个集合的反向顺序视图。

下面的程序说明了ConcurrentSkipListSet.Set()方法。

程序1 :

// Java Program Demonstrate descendingSet()
// method of ConcurrentSkipListSet */
import java.util.NavigableSet;
import java.util.Iterator;
import java.util.concurrent.ConcurrentSkipListSet;
  
class ConcurrentSkipListSetIteratorExample1 {
    public static void main(String[] args)
    {
  
        // Initializing the set
        ConcurrentSkipListSet<Integer>
            set = new ConcurrentSkipListSet<Integer>();
  
        // Adding elements to this set
        set.add(10);
        set.add(35);
        set.add(20);
        set.add(25);
  
        // Printing the elements of the set
        System.out.println("Contents of the set: " + set);
  
        // Creating a descending set object
        NavigableSet<Integer> des_set = set.descendingSet();
  
        // Printing the elements of the descending set
        System.out.println("Contents of the descending set: " 
                                                  + des_set);
    }
}

输出。

Contents of the set: [10, 20, 25, 35]
Contents of the descending set: [35, 25, 20, 10]

程序2： 演示原始集合的变化，同时在降序集合中插入元素的程序。

// Java Program Demonstrate descendingSet()
// method of ConcurrentSkipListSet */
import java.util.NavigableSet;
import java.util.Iterator;
import java.util.concurrent.ConcurrentSkipListSet;
  
class ConcurrentSkipListSetIteratorExample2 {
    public static void main(String[] args)
    {
  
        // Initializing the set
        ConcurrentSkipListSet<String>
            set = new ConcurrentSkipListSet<String>();
  
        // Adding elements to this set
        set.add("bob");
        set.add("alex");
        set.add("eric");
        set.add("chuck");
  
        // Creating a descending object
        NavigableSet<String> des_set = set.descendingSet();
  
        // Adding elements to the descending set and also to the set
        des_set.add("drake");
        des_set.add("fred");
  
        // Printing the elements of the set
        System.out.println("Contents of the set: " + set);
  
        // Printing the elements of the descending set
        System.out.println("Contents of the descending set: " 
                                                  + des_set);
    }
}

输出。

Contents of the set: [alex, bob, chuck, drake, eric, fred]
Contents of the descending set: [fred, eric, drake, chuck, bob, alex]

参考资料: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#descendingSet-