Java ConcurrentHashMap keys()用法及代码示例

Java中的ConcurrentHashMap类的keys()方法用于获取哈希图中存在的键的枚举。

用法:

Enumeration enu = ConcurrentHashMap.keys()

参数：该方法不带任何参数。

返回值：该方法返回ConcurrentHashMap的键的枚举。

下面的程序用于说明keys()方法的用法方式：

示例1:

// Java code to illustrate the keys() method 
  
import java.util.*; 
import java.util.concurrent.*; 
  
public class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty ConcurrentHashMap 
        ConcurrentHashMap<Integer, String> 
            hash_map = new ConcurrentHashMap<Integer, 
                                             String>(); 
  
        // Inserting elements into the map 
        hash_map.put(10, "Geeks"); 
        hash_map.put(15, "4"); 
        hash_map.put(20, "Geeks"); 
        hash_map.put(25, "Welcomes"); 
        hash_map.put(30, "You"); 
  
        // Displaying the ConcurrentHashMap 
        System.out.println("The Map is: " + hash_map); 
  
        // Creating an empty enumeration to store 
        Enumeration enu = hash_map.keys(); 
  
        System.out.println("The enumeration of keys are:"); 
  
        // Displaying the Enumeration 
        while (enu.hasMoreElements()) { 
            System.out.println(enu.nextElement()); 
        } 
    } 
}

输出：

The Map is: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The enumeration of keys are:
20
25
10
30
15

示例2:

// Java code to illustrate the keys() method 
  
import java.util.*; 
import java.util.concurrent.*; 
  
public class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty ConcurrentHashMap 
        ConcurrentHashMap<String, Integer> 
            hash_map = new ConcurrentHashMap<String, 
                                             Integer>(); 
  
        // Inserting elements into the table 
        hash_map.put("Geeks", 10); 
        hash_map.put("4", 15); 
        hash_map.put("Geeks", 20); 
        hash_map.put("Welcomes", 25); 
        hash_map.put("You", 30); 
  
        // Displaying the ConcurrentHashMap 
        System.out.println("The Map is: " + hash_map); 
  
        // Creating an empty enumeration to store 
        Enumeration enu = hash_map.keys(); 
  
        System.out.println("The enumeration of keys are:"); 
  
        // Displaying the Enumeration 
        while (enu.hasMoreElements()) { 
            System.out.println(enu.nextElement()); 
        } 
    } 
}

输出：

The Map is: {4=15, Geeks=20, You=30, Welcomes=25}
The enumeration of keys are:
4
Geeks
You
Welcomes

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 ConcurrentHashMap keys() 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。