Java中TreeMap的lastKey()方法: TreeMap.lastKey()

作者: Arvin Chen 分类: Java 来源: Break易站(www.breakyizhan.com)

java.util.TreeMap.lastKey()用于检索映射中存在的最后一个或最高密钥。

句法:

 tree_map.lastKey()

参数:该方法不接受任何参数。

返回值:该方法返回地图中的最后一个键。

异常:如果映射为空,则该方法抛出NoSuchElementException

下面的程序说明了java.util.TreeMap.lastKey()方法的工作原理

程序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

程序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
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