java.util.WeakHashMap.put() 方法

package com.codingdict;

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

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

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

      // checking Map
      System.out.println("Map: "+weakHashMap);

      // putting value at key 2
      String str = (String)weakHashMap.put("2", "newvalue");
      System.out.println("Returned value: "+str);
      System.out.println("New Map: "+weakHashMap);
   }    
}