Java TreeMap lastKey()用法及代码示例

java.util.TreeMap.lastKey()用于检索Map中存在的最后一个或最高键。

用法:

 tree_map.lastKey()

参数：该方法不带任何参数。

返回值：该方法返回映射中存在的最后一个键。

异常：如果映射为空，则该方法将引发NoSuchElementException。

以下程序说明了java.util.TreeMap.lastKey()方法的用法：
示例1:

// Java code to illustrate the lastKey() method 
import java.util.*; 
  
public class Tree_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty TreeMap 
        TreeMap<Integer, String> tree_map = new TreeMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        tree_map.put(10, "Geeks"); 
        tree_map.put(15, "4"); 
        tree_map.put(20, "Geeks"); 
        tree_map.put(25, "Welcomes"); 
        tree_map.put(30, "You"); 
  
        // Displaying the TreeMap 
        System.out.println("The Mappings are: " + tree_map); 
  
        // Displaying the lastKey of the map 
        System.out.println("The last key is " + tree_map.lastKey()); 
    } 
}

输出：

The Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The last key is 30

示例2:

// Java code to illustrate the lastKey() method 
import java.util.*; 
  
public class Tree_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty TreeMap 
        TreeMap<String, Integer> tree_map = new TreeMap<String, Integer>(); 
  
        // Mapping int values to string keys 
        tree_map.put("Geeks", 10); 
        tree_map.put("4", 15); 
        tree_map.put("Geeks", 20); 
        tree_map.put("Welcomes", 25); 
        tree_map.put("You", 30); 
  
        // Displaying the TreeMap 
        System.out.println("The Mappings are: " + tree_map); 
  
        // Displaying the lastKey of the map 
        System.out.println("The last key is " + tree_map.lastKey()); 
    } 
}

输出：

The Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
The last key is You

相关用法

注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 TreeMap lastKey() Method in Java。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。