4.2.4 集合Hashtable类

Hashtable 不仅能像Vetor那样存取对象 还可以给每一个对象指定一个key

Key和值都不能是空

不能有重复的key

 

定义方法  Hashtable has = new Hashtable();

添加值has.put("a", new Integer(1));

获取值Integer intHas = (Integer)has.get("a");

遍历值Enumeration en = has.keys();

              while(en.hasMoreElements()){

例子

    public static void main(String[] args) {

       Hashtable has = new Hashtable();

       has.put("a", new Integer(1));

       has.put("b", new Integer(2));

       has.put("c", new Integer(3));

       Integer intHas = (Integer)has.get("a");

      

       //遍历key

       Enumeration en = has.keys();

       while(en.hasMoreElements()){

           String key = (String)en.nextElement();

           System.out.print(key+"=");

           System.out.println(has.get(key));

       }

 

    }