java基础知识-map

public class  {
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("A", "01");
        map.put("B", "02");
        map.put("C", "03");
        
        Set<String> keySet = map.keySet();
        // 利用set集合的迭代器
        Iterator<String> iterator = keySet.iterator();
        while(iterator.hasNext()) {
            String key = iterator.next();
            String value = map.get(key);
            System.out.println("MAP INFO KEY:" + key + " VALUE:" + value);
        }
    }
}
``` 

> 方法二：

```java
public class QuickMap {
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("A", "01");
        map.put("B", "02");
        map.put("C", "03");
        // 通过entrySet()方法将map集合中的映射关系取出
        Set<Map.Entry<String, String>> entry = map.entrySet();
        // 利用关系集合entrySet的迭代器
        Iterator<Map.Entry<String, String>> iterator = entry.iterator();
        while(iterator.hasNext()) {
            // 获取Map.Entry的关系对象me
            Map.Entry<String, String> me = iterator.next();
            // 通过关系对象获取key
            String key = me.getKey();
            // 通过关系对象获取value
            String value = me.getValue();
            System.out.println("Key :" + key + " value :" + value);
        }
    }
}

public class CollectionMap {
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("A", "01");
        map.put("B", "02");
        map.put("C", "03");
        // Collection集合存放Map的value值
        Collection<String> collection = map.values();
        // 遍历Collection
        Iterator<String> it = collection.iterator();
        // 只能遍历value值，不能遍历key值
        while(it.hasNext()) {
            Object value = it.next();
            System.out.println(value);
        }
    }
}

public class BestMap {
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("A", "01");
        map.put("B", "02");
        map.put("C", "03");
        for (Map.Entry<String, String> entry : map.entrySet()) {
            System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
        }
    }
}