Java TreeSet descendingIterator()方法及示例

java.util.TreeSet <E> 类的 descendingIterator() 方法用来返回这个集合中的元素的迭代器，其顺序是降序。

语法：

public Iterator descendingIterator()

返回值： 该方法按降序返回该集合中元素的迭代器。

下面是说明 descendingIterator()方法的例子

例子1：

// Java program to demonstrate
// descendingIterator() 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);
 
            // Print the TreeSet
            System.out.println("TreeSet: " + treeadd);
 
            // create descending iterator
            // using descendingIterator() method
            Iterator<Integer>
                iterator = treeadd.descendingIterator();
 
            System.out.println("\nValues using DescendingIterator:");
 
            // printing the integrated value
            while (iterator.hasNext()) {
                System.out.println("Value : "
                                   + iterator.next());
            }
        }
 
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

TreeSet: [10, 20, 30, 40]

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

例2：

// Java program to demonstrate
// descendingIterator() 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);
 
            // create descending iterator
            // using descendingIterator() method
            Iterator<String>
                iterator = treeadd.descendingIterator();
 
            System.out.println("\nValues using DescendingIterator:");
 
            // printing the integrated value
            while (iterator.hasNext()) {
                System.out.println("Value : "
                                   + iterator.next());
            }
        }
 
        catch (Exception e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

TreeSet: [A, B, C, D]

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