Java Hashtable keys（）方法与示例

左手的ㄟ右手 2023-03-05 12:59 5阅读 0赞

## 哈希表类keys()方法 **(**Hashtable Class keys() method**)** ##

*  **keys() method** is available in java.util package.
    
    **keys()方法**在java.util包中可用。
 *  **keys() method** is used to returns keys of an enumeration in this Hashtable.
    
    **keys()方法**用于返回此Hashtable中的枚举键。
 *  **keys() method** is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
    
    **keys()方法**是一种非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。
 *  **keys() method** does not throw an exception at the time of returning keys of an enumeration.
    
    **keys()方法**在返回枚举键时不会引发异常。

**Syntax:**

**句法：**

public Enumeration keys();

**Parameter(s):**

**参数：**

*  It does not accept any parameter.
    
    它不接受任何参数。

**Return value:**

**返回值：**

The return type of the method is Enumeration, it returns set of keys of an enumeration in this Hashtable.

方法的返回类型为Enumeration ，它返回此Hashtable中的枚举键集。

**Example:**

**例：**

// Java program to demonstrate the example 
    // of Enumeration keys() method of Hashtable 
    
    import java.util.*;
    
    public class KeysOfHashtable {
        
        public static void main(String[] args) {
        
            //Instantiate a hashtable object  
            Hashtable ht = new Hashtable();
    
            // By using put() method is to
            // add the linked values in an
            // Hashtable ht
            ht.put(10, "C");
            ht.put(20, "C++");
            ht.put(30, "JAVA");
            ht.put(40, "PHP");
            ht.put(50, "SFDC");
    
            // Display Hashtable
            System.out.println("Hashtable: " + ht);
    
            // By using keys() method is to
            // returns the enumeration of all the
            // key exists in this Hashtable
    
            System.out.println("ht.keys(): ");
            for (Enumeration en = ht.keys(); en.hasMoreElements();) {
        
                System.out.println(en.nextElement());
            }
        }
    }

**Output**

**输出量**

Hashtable: {10=C, 20=C++, 30=JAVA, 40=PHP, 50=SFDC}
    ht.keys(): 
    10
    20
    30
    40
    50

> 翻译自: [https://www.includehelp.com/java/hashtable-keys-method-with-example.aspx][https_www.includehelp.com_java_hashtable-keys-method-with-example.aspx]

[https_www.includehelp.com_java_hashtable-keys-method-with-example.aspx]: https://www.includehelp.com/java/hashtable-keys-method-with-example.aspx