2020-02-21Map 接口

1.保存形式
Key ---> value 的保存方式 键值对
2.常用子类
HashMap：无序存放，key不允许重复
HashTable： 无序存放，key不允许重复

2.1Map的使用方法

public class MapDemo01 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Map<String,String> map = new HashMap<String,String>();
        map.put("key1","fjasmin");
        map.put("key2","shlearry");
        map.put("key3","anke");
        map.put("key4","fangjian");
        map.put("key5","hanxi");
        map.put("key6","ye");
        String str = map.get("key6");
        System.out.println(str);
    }

}

2.2 判断map中是否含有键值对

public class MapDemo2 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Map<String,String> map = new HashMap<String,String>();
        map.put("key1","fjasmin");
        map.put("key2","shlearry");
        map.put("key3","anke");
        map.put("key4","fangjian");
        map.put("key5","hanxi");
        map.put("key6","ye");
        /*
         * String str = map.get("key6"); System.out.println(str);
         */
        if(map.containsKey("key1")) {
            System.out.println("key keep!");
        }else {
            System.out.println("key lost!");
        }
        
        if(map.containsValue("fjasmin")) {
            System.out.println("value keep!");
        }else {
            System.out.println("value lost!");
        }
    }

}

2.3遍历取出Map中的键值对

public class MapDemo3 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Map<String,String> map = new HashMap<String,String>();
        map.put("key1","fjasmin");
        map.put("key2","shlearry");
        map.put("key3","anke");
        map.put("key4","fangjian");
        map.put("key5","hanxi");
        map.put("key6","ye");
        
         Set<String> s = map.keySet();
         Iterator<String> iter = s.iterator();
         while(iter.hasNext()) 
         { System.out.println(iter.next()); }
         
        Collection<String> collection = map.values();
        Iterator<String> iter1 = collection.iterator();
        while(iter1.hasNext()) {
            System.out.println(iter1.next());
        }
    }

}