hashmapdemo.java

Java面向对象编程(随书配套源代码) 阐述了面向对象编程的思想

package chapter8;

import java.util.*;

class HashMapDemo
{
    public static void main(String args[])
    {
        HashMap hm = new HashMap();
        hm.put("John Doe", new Double(3434.34));
        hm.put("Tom Smith", new Double(123.22));
        hm.put("Jane Baker", new Double(1378.00));
        hm.put("Todd Hall", new Double(99.22));
        hm.put("Ralph Smith", new Double(-19.08));
        Set set = hm.entrySet();
        Iterator i = set.iterator();
        while(i.hasNext())
        {
            Map.Entry me = (Map.Entry)i.next();
            System.out.print(me.getKey() + ": ");
            System.out.println(me.getValue());
        }
        System.out.println();
        double balance = ((Double)hm.get("John Doe")).doubleValue();
        hm.put("John Doe", new Double(balance + 1000));
        System.out.println("John Doe's new balance: " +
        hm.get("John Doe"));
    }
}