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

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

  isEmpty()方法在java.util包中可用。

• isEmpty() method is used to check whether this Hashtable maps no key-value pairs or not.

  isEmpty()方法用于检查此Hashtable是否不映射任何键-值对。

• isEmpty() 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.

  isEmpty()方法是一个非静态方法，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。

• isEmpty() method does not throw an exception at the time of checking the empty status of this Hashtable.

  在检查此哈希表的空状态时， isEmpty()方法不会引发异常。

Syntax:

句法：

public boolean isEmpty();

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 boolean, it returns true when this Hashtable has no key-value pairs otherwise it returns false.

方法的返回类型为boolean ，如果此哈希表没有键值对，则返回true，否则返回false。

Example:

例：

// Java program to demonstrate the example // of boolean isEmpty() method of Hashtable import java.util.*;public class IsEmptyOfHashtable {
       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 isEmpty() method is to        // check whether key-value pairs exists         // or not in this Hashtable        boolean status = ht.isEmpty();        // Display status        System.out.println("ht.isEmpty(): " + status);    }}

Output

输出量

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

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