遍历map的四种方式

1. 通过Map.ketSet遍历key和value
2. 通过Iterator迭代器遍历循环Map.entrySet().iterator
3. 通过Map.entrySet遍历key和value
4. 通过Map.value遍历所有value，但不能遍历key

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


public class Map01 {

    public static void main(String[] args) {
        Map map = new HashMap();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");

        System.out.println("通过Map.ketSet遍历key和value");
        for (String key : map.keySet()) {
            System.out.println("key=" + key + ",value=" + map.get(key));
        }

        System.out.println("通过Iterator迭代器遍历循环Map.entrySet().iterator");
        Iterator> iterator = map.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry next = iterator.next();
            System.out.println("key=" + next.getKey() + ",value=" + next.getValue());
        }

        System.out.println("通过Map.entrySet遍历key和value");
        for (Map.Entry entry : map.entrySet()) {
            System.out.println("key=" + entry.getKey() + ",value=" + entry.getValue());
        }

        System.out.println("通过Map.value遍历所有value，但不能遍历key");
        for (String value : map.values()) {
            System.out.println("value=" + value);
        }
    }
}