哈希表类keySet()方法 (Hashtable Class keySet() method)

• keySet() method is available in java.util package.

  keySet()方法在java.util包中可用。

• keySet() method is used to return a set of keys to be viewed in a set in this Hashtable.

  keySet()方法用于返回要在此Hashtable集中的一组键中查看的键。

• keySet() 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.

  keySet()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名访问该方法，则会收到错误消息。

• keySet() method does not throw an exception at the time of returning keys in a set view.

  在设置视图中返回键时， keySet()方法不会引发异常。

Syntax:

句法：

public Set keySet();

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 Set, it returns keys in a set view of this Hashtable.

方法的返回类型为Set ，它在此Hashtable的set视图中返回键。

Example:

例：

// Java program to demonstrate the example // of Set keySet() method of Hashtable import java.util.*;public class KeySetOfHashtable {
       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 keySet() method is to        // return th set of keys exists in        // Hashtable to be viewed in a set        Set s = ht.keySet();        // Display Hashtable in a set view        System.out.println("ht.keySet(): " + s);    }}

Output

输出量

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

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