键值对
map会将同名的值覆盖掉
public static void main(String[] args) {
Map<String,String> maptest=new HashMap<String,String>();
maptest.put("hello", "你好!");
System.out.println("maptest=>"+maptest);
maptest.put("hello", "world");
System.out.println("maptest=>"+maptest);
System.out.println(maptest.get("hello"));
}