java.util.IdentityHashMap.containsKey() 方法

package com.codingdict;

import java.util.*;

public class IdentityHashMapDemo {
   public static void main(String args[]) {

      // create identity hash map
      IdentityHashMap ihmap = new IdentityHashMap();

      // populate the map
      ihmap.put(1, "java");
      ihmap.put(2, "util");
      ihmap.put(3, "package");

      // check if key 3 exists
      boolean isavailable = ihmap.containsKey(3);

      System.out.println("Is key '3' exists: " + isavailable);
   }    
}