Map集合

Map<String, Student> m = new Hashtable<String,Student>();

每一个key的值都不一样，否则指向的是同一个value。但是value可以一样。

来看一个简单的代码：

 @Test
   public void test() {
	   Map<String, Student> m = new Hashtable<String,Student>();
	   m.put("qqqqq",new Student("ww",34));  //存入索引和值
	  Student s = m.get(new String("qqqqq"));
	  Student ss = m.get("qqqqq");
	  System.out.println(s.getName());
	  System.out.println(ss.getAge());
   }

输出结果为：

再来看一个输出key的值，value的值，key和value一块输出的值。

@Test
   public void test1() {
	   Map<String, Student> m = new Hashtable<String,Student>();
	   m.put("A",new Student("ww",32));
	   m.put("B",new Student("ww",35));
	   m.put("C",new Student("ww",323));
	   
	   m.put("D",new Student("ww",34));
	   m.put("E",new Student("ww",39));
	   //得到key
	   Set<String> s = m.keySet();
	   for(Iterator<String> iter = s.iterator();iter.hasNext();) {
		   System.out.println(iter.next());
	   }
	   //得到value
	   Collection<Student> s1 = m.values();
	   for(Iterator<Student> iter = s1.iterator();iter.hasNext();) {
		   System.out.println(iter.next());
	   }
	   //key和value一块输出（entry）
	 Collection<Entry<String, Student>> s2 = m.entrySet();
	   for(Iterator<Entry<String, Student>> iter = s2.iterator();iter.hasNext();) {
		   Entry<String, Student> e = iter.next();
		   System.out.println(e.getKey()+":"+e.getValue());
	   }
   }