Java 集合 检查HashMap是否为空

用于检查HashMap是否为空的程序。我们使用HashMap类的isEmpty()方法来执行此检查。

程序

import java.util.HashMap;class HashMapIsEmptyExample{  public static void main(String args[]) {    // Create a HashMap    HashMap<Integer, String> hmap = new HashMap<Integer, String>();     // Checking whether HashMap is empty or not    /* isEmpty() method signature and description -     * public boolean isEmpty(): Returns true if this map      * contains no key-value mappings.     */    System.out.println("Is HashMap Empty? "+hmap.isEmpty());    // Adding few elements    hmap.put(11, "Jack");    hmap.put(22, "Rock");    hmap.put(33, "Rick");    hmap.put(44, "Smith");    hmap.put(55, "Will");    // Checking again    System.out.println("Is HashMap Empty? "+hmap.isEmpty());  } }

输出：

Is HashMap Empty? trueIs HashMap Empty? false