Java并发-13.ThreadLocal

import java.util.concurrent.TimeUnit;

/**
 * end()方法返回从begin()方法调用开始到end()方法被调用时的时间差
 *
 * @author pengjunzhe
 */
public class Profiler {
    /**
     * 第一次调用get()方法会进行初始化(如果set方法没有调用)，每个线程调用一次
     */
    private static final ThreadLocal<Long> TIME_THREAD_LOCAL = new ThreadLocal<Long>() {
        @Override
        protected Long initialValue() {
            return System.currentTimeMillis();
        }
    };

    public static final void begin() {
        TIME_THREAD_LOCAL.set(System.currentTimeMillis());
    }

    public static final long end() {
        return System.currentTimeMillis() - TIME_THREAD_LOCAL.get();
    }

    public static void main(String[] args) throws Exception {
        Profiler.begin();
        TimeUnit.SECONDS.sleep(1);
        System.out.println("Cost: " + Profiler.end() + " mills");
    }
}