import java.util.HashMap;
import java.util.Map;

public class Map1
{
	public static void main(String[] args) 
	{
		Map<String, String> map = new HashMap<String, String>();
		map.put("aa","AA");//put返回值為值的型別
		map.put("bb","BB");//前鍵  後值  鍵不能重複 值可以重複
		map.put("ee","BB");
		map.put("cc","CC");
		map.put("dd","DD");
		System.out.println("put return  "+map.put("aa","A"));
		System.out.println(map);//HashMap無序
		//put的返回值為  AA，aa鍵的值  A把AA 趕跑了
//		Map<String, String> map2 = new HashMap<String, String>();
//		map2.put("ee","EE");
//		map2.put("ff","FF");
		System.out.println("remove return   "+map.remove("ee"));//根據鍵刪除一條map中的資料，返回的是該鍵對應的值
		System.out.println(map);
		//map.clear();
		System.out.println("clear沒有返回值，此時map中為："+map);
		System.out.println("判斷map中是否包含指定的鍵 ee   "+map.containsKey("aa"));
		System.out.println("判斷map中是否包含指定的值    "+map.containsValue("a"));
		System.out.println("空嗎  "+map.isEmpty());
		map.clear();
		map.put(null, null);
		System.out.println("空嗎  "+map.isEmpty());
		System.out.println(map);
	}
}