Hashtable测试

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本文详细探讨了Java中的Hashtable类，包括其基本原理、操作方法以及在并发环境下的表现。通过实例代码，展示了Hashtable的使用方式，同时对比了它与HashMap的区别，帮助读者理解何时选择使用Hashtable。

                                                   Hashtable测试

package src.main.java.com.qqjx.thread;


/*
 * @Auther  wangpeng
 * @Date 2021/1/31
 */

public class Constants {

    public static final int COUNT = 1000000;
    public static final int THREAD_COUNT = 100;

}

package src.main.java.com.qqjx.thread;

import java.util.Hashtable;
import java.util.UUID;

/*
 * @Auther  wangpeng
 * @Date 2021/1/31
 */

public class T01_TestHashtable {

    static Hashtable<UUID, UUID> m = new Hashtable<>();

    static int count = Constants.COUNT;
    static UUID[] keys = new UUID[count];
    static UUID[] values = new UUID[count];
    static final int THREAD_COUNT = Constants.THREAD_COUNT;

    static {
        for (int i = 0; i < count; i++) {
            keys[i] = UUID.randomUUID();
            values[i] = UUID.randomUUID();
        }
    }

    static class MyThread extends Thread {
        int start;
        int gap = count/THREAD_COUNT;

        public MyThread(int start) {
            this.start = start;
        }

        @Override
        public void run() {
            for(int i=start; i<start+gap; i++) {
                m.put(keys[i], values[i]);
            }
        }
    }

    public static void main(String[] args) {

        long start = System.currentTimeMillis();

        Thread[] threads = new Thread[THREAD_COUNT];

        for(int i=0; i<threads.length; i++) {
            threads[i] =
                    new MyThread(i * (count/THREAD_COUNT));
        }

        for(Thread t : threads) {
            t.start();
        }

        for(Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long end = System.currentTimeMillis();
        System.out.println(end - start);

        System.out.println(m.size());

        //-----------------------------------

        start = System.currentTimeMillis();
        for (int i = 0; i < threads.length; i++) {
            threads[i] = new Thread(()->{
                for (int j = 0; j < 10000000; j++) {
                    m.get(keys[10]);
                }
            });
        }

        for(Thread t : threads) {
            t.start();
        }

        for(Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        end = System.currentTimeMillis();
        System.out.println(end - start);
    }

}

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