Hashmap使用

package base.map;

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/**
 * HashMap使用举例
 * 
 * @author pengch
 * 
 */
public class HashMapExample {

 public static void main(String[] args) {

  Map m1 = new HashMap();
  m1.put("Chinese", new Long(100000));
  m1.put("English", new Long(20000));
  m1.put("French", new Long(3000));
  m1.put("Korean", new Long(400));

  System.out.println("The HashMap holds " + m1.size() + " elements");

  System.out.println("The keys are:");

  // 因为Map的key不可能重复，所以，可以用Set数据结构来存储
  Set keySet = m1.keySet();
  Iterator ikey = keySet.iterator();
  while (ikey.hasNext()) {
   System.out.println("\t" + ikey.next());
  }

  System.out.println("The values are:");

  // 因为Map的值有可能重复，所以不能用Set，要用Collection
  Collection valueCol = m1.values();
  Iterator ival = valueCol.iterator();
  while (ival.hasNext()) {
   System.out.println("\t" + ival.next());
  }

  // 根据key，取出特定的值
  System.out.println("The value for Key \"Korean\" is "
    + m1.get("Korean").toString());
 }

}