map 几种遍历性能比较

忘是亡心i 2021-12-22 11:47 358阅读 0赞

public class MyDemo001 {
        private static final Logger log = LoggerFactory.getLogger(MyDemo001.class);
        public static void main(String[] args) {
            Map<Integer,Integer> map = new HashMap<>();
            for(int i =0;i<100000;i++){
                map.put(i,i);
            }
    
            long end = System.currentTimeMillis();
            map.entrySet().forEach(endrt->{
                new String();
            });
            long start = System.currentTimeMillis();
            log.info("entrySet.forEach :::::>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时："+(start-end));
    
            for(Integer s:map.keySet()){
    //            System.out.println("key : "+s+" value : "+map.get(s));
                new String();
            }
            end = System.currentTimeMillis();
            log.info("map.keySet()>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时："+(end-start));
            for(Map.Entry<Integer, Integer> entry : map.entrySet()){
    //            System.out.println("键 key ："+entry.getKey()+" 值value ："+entry.getValue());
                new String();
            }
            start = System.currentTimeMillis();
            log.info("Map.Entry()>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时："+(start-end));
    
    
            Iterator<Map.Entry<Integer, Integer>> it=map.entrySet().iterator();
            while(it.hasNext()){
                Map.Entry<Integer, Integer> entry=it.next();
    //            System.out.println("键key ："+entry.getKey()+" value ："+entry.getValue());
                new String();
                }
            end = System.currentTimeMillis();
            log.info("Iterator  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时："+(end-start));
        }
    
    
    }

结果输出：

[INFO] entrySet.forEach :::::>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时：48
    [INFO] map.keySet()>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时：6
    [INFO] Map.Entry()>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时：4
    [INFO] Iterator  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>总耗时：2

综合：

Iterator>Map.Entry()>map.keySet()>entrySet.forEach

转载于:https://www.cnblogs.com/Absorbed/p/10487422.html