Java TreeSet descendingSet()用法及代码示例

java.util.TreeSet类的descendingSet()方法用于返回此集合中包含的元素的逆序视图。降序集由该集支持，因此对该集的更改会反映在降序集中，反之亦然。如果在进行任何一个集合的迭代时修改了任何一个集合(通过迭代器自己的remove操作除外)，则迭代的结果是不确定的。

返回的集合的排序与Collections.reverseOrder(comparator())等效。表达式s.descendingSet().descendingSet()返回s的视图，该视图与s基本等效。

用法:

public NavigableSet descendingSet()

返回值：此方法返回此集合的逆序视图。

以下示例说明了descendingSet()方法

示例1:

// Java program to demonstrate 
// descendingSet() method 
// for String value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
        throws Exception 
    { 
        try { 
  
            // create tree set object 
            TreeSet<String> treeadd = new TreeSet<String>(); 
  
            // populate the TreeSet using add() method 
            treeadd.add("A"); 
            treeadd.add("B"); 
            treeadd.add("C"); 
            treeadd.add("D"); 
  
            // Print the TreeSet 
            System.out.println("TreeSet: " + treeadd); 
  
            // getting the reverse order view of element 
            // using descendingSet() method 
            NavigableSet<String> 
                treereverse = treeadd.descendingSet(); 
  
            // getting iterated view of NavigableSet 
            Iterator<String> iterator = treereverse.iterator(); 
  
            System.out.println("\nValues using DescendingSet:"); 
  
            // printing the interated value 
            while (iterator.hasNext()) { 
                System.out.println("Value : "
                                   + iterator.next()); 
            } 
        } 
  
        catch (NullPointerException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

输出：

TreeSet: [A, B, C, D]

Values using DescendingSet:
Value : D
Value : C
Value : B
Value : A

示例2:

// Java program to demonstrate 
// descendingSet() method 
// for Integer value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) throws Exception 
    { 
        try { 
  
            // create tree set object 
            TreeSet<Integer> treeadd = new TreeSet<Integer>(); 
  
            // populate the TreeSet using add() method 
            treeadd.add(10); 
            treeadd.add(20); 
            treeadd.add(30); 
            treeadd.add(40); 
  
            // getting the reverse order view of element 
            // using descendingSet() method 
            NavigableSet<Integer> treereverse = treeadd.descendingSet(); 
  
            // getting iterated view of NavigableSet 
            Iterator<Integer> iterator = treereverse.iterator(); 
  
            System.out.println("\nValues using DescendingSet:"); 
  
            // printing the interated value 
            while (iterator.hasNext()) { 
                System.out.println("Value : " + iterator.next()); 
            } 
        } 
  
        catch (NullPointerException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

输出：

Values using DescendingSet:
Value : 40
Value : 30
Value : 20
Value : 10

相关用法

注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 TreeSet descendingSet() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。