Java中TreeMap navigableKeySet()方法的示例

navigableKeySet() 方法是java.util.TreeMap类中的一个方法，用于返回此映射中包含的键的可导航集视图。
这个集合的迭代器按升序返回键。该集合受到地图的支持，因此地图的更改会反映在集合中，反之亦然。如果在迭代器的remove操作之外进行了对映射的迭代，则迭代的结果是未定义的。该集合支持元素删除，通过Iterator.remove，Set.remove，removeAll，retainAll和clear操作从地图中删除相应的映射。它不支持add或addAll操作。
语法:

public NavigableSet navigableKeySet()

返回值: 此方法返回一个NavigableSet视图，包含此映射中的键。
以下是用于说明navigableKeySet()方法的示例：
示例 1:

//Java演示程序
//使用navigableKeySet()方法
//适用于Integer值键

import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {

        try {

            // creating object of TreeMap<Integer, String>
            TreeMap<Integer, String>
                treemap = new TreeMap<Integer, String>();

            // populating tree map
            treemap.put(1, "One");
            treemap.put(2, "Two");
            treemap.put(3, "Three");
            treemap.put(4, "Four");
            treemap.put(5, "Five");

            // printing the TreeMap
            System.out.println("TreeMap: " + treemap);

            // getting navigable set view of the keys
            // using navigableKeySet() method
            NavigableSet<Integer>
                value = treemap.navigableKeySet();

            // printing the value
            System.out.println("Value is: " + value);
        }

        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five}
Value is: [1, 2, 3, 4, 5]

示例 2:

// Java program to demonstrate
// navigableKeySet() method
// for String value key
 
import java.util.*;
 
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
 
        try {
 
            // creating object of TreeMap<Integer, String>
            TreeMap<String, Integer>
                treemap = new TreeMap<String, Integer>();
 
            // populating tree map
            treemap.put("A", 1);
            treemap.put("B", 2);
            treemap.put("C", 3);
            treemap.put("D", 4);
            treemap.put("E", 5);
 
            // printing the TreeMap
            System.out.println("TreeMap: " + treemap);
 
            // getting navigable set view of the keys
            // using navigableKeySet() method
            NavigableSet<String>
                value = treemap.navigableKeySet();
 
            // printing the value
            System.out.println("Value is: " + value);
        }
 
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

TreeMap: {A=1, B=2, C=3, D=4, E=5}
Value is: [A, B, C, D, E]