Java Hashtable keys()用法及代码示例

Java中Hashtable类的java.util.Hashtable.keys()方法用于获取哈希表中存在的键的枚举。

用法:

Enumeration enu = Hash_table.keys()

参数：该方法不带任何参数。

返回值：该方法返回哈希表的键的枚举。

以下程序用于说明java.util.Hashtable.keys()方法的用法：
示例1:

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

输出：

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

示例2:

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

输出：

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

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 Hashtable keys() 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。