java.util.HashMap.put() 方法

package com.codingdict;

import java.util.*;

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

      // create hash map
      HashMap newmap = new HashMap();

      // populate hash map
      newmap.put(1, "tutorials");
      newmap.put(2, "point");
      newmap.put(3, "is best");

      System.out.println("Map value before change: "+ newmap);

      // put new values at key 3
      String prevvalue = (String)newmap.put(3,"is great");

      // check returned previous value
      System.out.println("Returned previous value: "+ prevvalue);

      System.out.println("Map value after change: "+ newmap);
   }    
}