Map 方法记录

Map<Object,Object> map = new HashMap<>();
map.put("hello", "hello");
map.put("world","world");
map.put("world","world1");  
//注意，Map的键不能重复，只能存储一个，存储的是map.put("world","world1");  

1. 获取Map中key的集合
Set set = map.entrySet();

2. 获取Map中value的集合
Collection collet = map.values();

Set set = map.keySet();
for (Iterator iterator = set.iterator(); iterator.hasNext();){
//先获取键的Set，然后根据键去取值
    Object key = iterator.next();
    String value = (String)map.get(key);
    System.out.println(key + " =" + value);
}

HashMap map = new HashMap();
map.put("a","aa");
map.put("b","bb");
map.put("c","cc");

Set set = map.entrySet();
for (Iterator iterator = set.iterator(); iterator.hasNext();){
//直接获取Map.Entry 
    Map.Entry obj = (Map.Entry) iterator.next();
    System.out.println(obj.getKey());
    System.out.println(obj.getValue());
}

Map<String, String> map = new HashMap<String, String>();
map.put("Java入门教程", "http://c.biancheng.net/java/");
map.put("C语言入门教程", "http://c.biancheng.net/c/");

for (Map.Entry<String, String> entry : map.entrySet()) {
    String mapKey = entry.getKey();
    String mapValue = entry.getValue();
    System.out.println(mapKey + "：" + mapValue);
}