java map对象的效率比较

来源：互联网发布：数组转字符串编辑：程序博客网时间：2024/06/10 08:45

@SuppressWarnings("unchecked")
public class MapPerformance {
    public static void main(String[] args) {
        MapPerformance test = new MapPerformance(10 * 10000);
        out.print(StringUtils.center("Test Map Performance: loop=" + test.loop, 80, '-'));
        out.printf("\n sssssss", "", "put", "put", "remove", "get",
                "iterator","for");
        test.benchmark(new HashMap());
        test.benchmark(new Hashtable());
        test.benchmark(new LinkedHashMap());
        test.benchmark(new IdentityHashMap());
        test.benchmark(new TreeMap());
        test.benchmark(new WeakHashMap());
        test.benchmark(new ConcurrentHashMap());
    }

    private int loop = 10000;
    public MapPerformance(int loop) {
        this.loop = loop;
    }
    public void benchmark(Map map) {
        out.printf("\n s", map.getClass().getSimpleName());
        int j;
        StopWatch watch = null;
        //1.测试顺序性能(Add)
        (watch = new StopWatch()).start();
        for (int i = 0; i < loop; i++) {
        map.put(i, i);
        }
        watch.stop();
        out.printf("d", watch.getTime());
        //2.测试随机插入性能(Random insert)
        (watch = new StopWatch()).start();
        for (int i = 0; i < loop; i++) {
            j = (int) (Math.random() * loop);
            map.put(j, new Integer(-j));
        }
        watch.stop();
        out.printf("d", watch.getTime());
        //3.测试随机索引删除(Random remove)
        (watch = new StopWatch()).start();
        for (int i = 0; i < loop; i++) {
            j = (int) (Math.random() * loop);
            map.remove(j);
        }
        watch.stop();
        out.printf("d", watch.getTime());
        //4.测试随机取数性能(Random get)
        (watch = new StopWatch()).start();
        for (int i = 0; i < loop; i++) {
            j = (int) (Math.random() * loop);
            map.get(j);
        }
        watch.stop();
        out.printf("d", watch.getTime());

        //6.测试迭代性能(Iterator)
        (watch = new StopWatch()).start();
        Iterator<Object> iter = map.values().iterator();
        while (iter.hasNext()) {
            iter.next();
        }
        watch.stop();
        out.printf("d", watch.getTime());
      //7.测试迭代性能(Iterator)
        (watch = new StopWatch()).start();
     //   Iterator<Object> iter = list.iterator();
        for (Object obj : map.values()) {

        }
        watch.stop();
        out.printf("d", watch.getTime());
    }

}
结果：

-----------------------Test Map Performance: loop=100000------------------------
                           put    random-put    remove       get iterator       for
             HashMap        47        94        78        47         0         0
           Hashtable       141        78        78        62         0        16
       LinkedHashMap       125        78        94        47         0         0
     IdentityHashMap       172       265        47        63        15        16
             TreeMap        94       125       187       109         0         0
         WeakHashMap       156       250        47        31         0        16
   ConcurrentHashMap        94       140        79        46         0        16

结论：

1、HashMap的性能比较高，但不是线程安全的

2、ConcurrentHashMap的put性能没有HashMap的高，get的性能与HashMap一样或者略高于，但是是线程安全的

参考：http://blog.sina.com.cn/s/blog_56fd58ab0100qel3.html