遍历Map集合的几种方式

1. 迭代器(Iterator)
2. for
3. lambda
4. Stream

代码示例

package com.haimeng.Array;import java.security.Key;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;public class Lambda1 {public static void main(String[] args) {// 创建并赋值 HashMapMap<Integer, String> map = new HashMap();map.put(1, "Java");map.put(2, "JDK");map.put(3, "Spring Framework");map.put(4, "MyBatis framework");map.put(5, "Java中文社群");//1\ Lambda 进行遍历map.forEach((key, value) -> {System.out.println(key);System.out.println(value);});//2\ forEach EntrySet 进行遍历for(Map.Entry<Integer,String> entry : map.entrySet()){System.out.println(entry.getKey());System.out.println(entry.getValue());}//3\ forEach KeySet进行遍历for(Integer Key : map.keySet()){System.out.println(Key);System.out.println(map.get(Key));}//4\ Iterator EntrySet进行遍历Iterator<Map.Entry<Integer, String>> iterator = map.entrySet().iterator();while (iterator.hasNext()){Map.Entry<Integer, String> entry = iterator.next();System.out.println(entry.getKey());System.out.println(entry.getValue());}//5\ Iterator KeySet进行遍历Iterator<Integer> iterator1 = map.keySet().iterator();while (iterator1.hasNext()){Integer key = iterator1.next();System.out.println(key);System.out.println(map.get(key));}// 6\ Streams API 单线程进行遍历map.entrySet().stream().forEach((entry) ->{System.out.println(entry.getKey());System.out.println(entry.getValue());});//7\ Streams API 多线程进行遍历map.entrySet().parallelStream().forEach((entry) ->{System.out.println(entry.getKey());System.out.println(entry.getValue());});}
}