Map集合

遍历map集合有三种:

1.通过map.keySet()获取key的Set集合;

2.通过map.values()获取所有的value的Collection集合;

3.通过map.entrySet()获取所有的键值对Set集合;

获取key,value的集合后通过迭代器Iterator遍历;

实例代码:

Map<String,Object> map = new HashMap();
map.put("1",1);
map.put("2",'s');
map.put("3","z");
map.put("4",true);
map.put(null,"0");

/**
 * Map.keyset 获取key的集合
 */
Set<String> keySet = map.keySet();
Iterator<String> iterator = keySet.iterator();
while (iterator.hasNext()){
    String next = iterator.next();
    Object o = map.get(next);
    System.out.println(o);
}

/**
 *  获取value的集合
 */
Collection<Object> values = map.values();
Iterator<Object> it = values.iterator();
while (it.hasNext()){
    Object next = it.next();
    System.out.println(next);
}

/**
 * 获取key-value键值对集合
 */
Set<Map.Entry<String, Object>> entries = map.entrySet();
Iterator<Map.Entry<String, Object>> ite = entries.iterator();
while (ite.hasNext()){
    Map.Entry<String, Object> next = ite.next();
    System.out.println(next.getKey()+": "+next.getValue());
}