Java Dictionary keys()用法及代码示例

Java中的Dictionary类的keys()方法用于获取字典中存在的键的枚举。

用法:

Enumeration enu = DICTIONARY.keys()

参数：该方法不带任何参数。

返回值：该方法返回字典键的枚举。

下面的程序用于说明java.util.Dictionary.keys()方法的用法：
示例1:

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

输出：

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

输出：

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

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注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 Dictionary 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。