jdk 1.8 后stream 流 map 循环 推荐

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

public class text1 {
    public static void main(String[] args) {

        Map<String, String> data = new HashMap<>();
        data.put("11", "22");
        data.put("22", "44");
        data.put("33", "55");
        data.put("44", "66");


        // 1  Stream 流 forEach
        data.forEach((key, value) -> {
            System.out.println(key + "---" + value);
        });


        // 2  keySet方法取出所有的可以
        Set<String> set = data.keySet();
        for (String key : data.keySet()) {
            System.out.println("key:" + key + "value:" + data.get(key));
        }
        // 3 迭代器 进行取值  iterator
        Iterator<Map.Entry<String, String>> map = data.entrySet().iterator();
        //while 遍历
        while (map.hasNext()){
            Map.Entry<String, String> next = map.next();
            System.out.println("key :"+ next.getKey()+"value :"+next.getValue());
        }

        //使用entrySet 进行遍历 (entrySet（） 返回一个包含映射关系的Set集合)
        for (Map.Entry<String, String> entry : data.entrySet()) {
            System.out.println("key: "+ entry.getKey()+ "value: "+entry.getValue());
        }
    }

}

以下是输出的结果

11---22
22---44
33---55
44---66

key:11value:22
key:22value:44
key:33value:55
key:44value:66

key :11value :22
key :22value :44
key :33value :55
key :44value :66

key: 11value: 22
key: 22value: 44
key: 33value: 55
key: 44value: 66

以上是map 循环的4 种方式