java.util.WeakHashMap.keySet() 方法

package com.codingdict;

import java.util.Map;
import java.util.WeakHashMap;
import java.util.Set;

public class WeakHashMapDemo {
   public static void main(String[] args) {
      Map<String, String> weakHashMap = new WeakHashMap<String, String>();

      // put keys and values in the Map      
      weakHashMap.put("1", "first");
      weakHashMap.put("2", "two");
      weakHashMap.put("3", "three");

      // printing the contents of the Map
      System.out.println("Contents of the Map");
      System.out.println(weakHashMap);

      // populating the set
      Set set = weakHashMap.keySet();
      System.out.println("Contents of the set");
      System.out.println(set);
   }     
}