public final int getAndIncrement() {
    for (;;) {
      int current = get();
      int next = current + 1;
      if (compareAndSet(current, next))
        return current;
    }
}

public class CASDemo {
  private final int THREAD_NUM = 1000;
  private final int MAX_VALUE = 20000000;
  private AtomicInteger casI = new AtomicInteger(0);
  private int syncI = 0;
  private String path = "/Users/pingping/DataCenter/Books/Linux/Linux常用命令详解.txt";

  public void casAdd() throws InterruptedException {
    long begin = System.currentTimeMillis();
    Thread[] threads = new Thread[THREAD_NUM];
    for (int i = 0; i < THREAD_NUM; i++) {
      threads[i] = new Thread(new Runnable() {
        public void run() {
          while (casI.get() < MAX_VALUE) {
            casI.getAndIncrement();
          }
        }
      });
      threads[i].start();
    }
    for (int j = 0; j < THREAD_NUM; j++) {
      threads[j].join();
    }
    System.out.println("CAS costs time: " + (System.currentTimeMillis() - begin));
  }

  public void syncAdd() throws InterruptedException {
    long begin = System.currentTimeMillis();
    Thread[] threads = new Thread[THREAD_NUM];
    for (int i = 0; i < THREAD_NUM; i++) {
      threads[i] = new Thread(new Runnable() {
        public void run() {
          while (syncI < MAX_VALUE) {
            synchronized ("syncI") {
              ++syncI;
            }
          }
        }
      });
      threads[i].start();
    }
    for (int j = 0; j < THREAD_NUM; j++)
      threads[j].join();
    System.out.println("sync costs time: " + (System.currentTimeMillis() - begin));
  }
}

14           while (casI.get() < MAX_VALUE) {
15             casI.getAndIncrement();
16           }

public class CASDemo {
  private final int THREAD_NUM = 1000;
  private final int MAX_VALUE = 1000;
  private AtomicInteger casI = new AtomicInteger(0);
  private int syncI = 0;
  private String path = "/Users/pingping/DataCenter/Books/Linux/Linux常用命令详解.txt";

  public void casAdd2() throws InterruptedException {
    long begin = System.currentTimeMillis();
    Thread[] threads = new Thread[THREAD_NUM];
    for (int i = 0; i < THREAD_NUM; i++) {
      threads[i] = new Thread(new Runnable() {
        public void run() {
          while (casI.get() < MAX_VALUE) {
            casI.getAndIncrement();
            try (InputStream in = new FileInputStream(new File(path))) {
                while (in.read() != -1);
            } catch (IOException e) {
              e.printStackTrace();
            }
          }
        }
      });
      threads[i].start();
    }
    for (int j = 0; j < THREAD_NUM; j++)
      threads[j].join();
    System.out.println("CAS Random costs time: " + (System.currentTimeMillis() - begin));
  }

  public void syncAdd2() throws InterruptedException {
    long begin = System.currentTimeMillis();
    Thread[] threads = new Thread[THREAD_NUM];
    for (int i = 0; i < THREAD_NUM; i++) {
      threads[i] = new Thread(new Runnable() {
        public void run() {
          while (syncI < MAX_VALUE) {
            synchronized ("syncI") {
              ++syncI;
            }
            try (InputStream in = new FileInputStream(new File(path))) {
              while (in.read() != -1);
            } catch (IOException e) {
              e.printStackTrace();
            }
          }
        }
      });
      threads[i].start();
    }
    for (int j = 0; j < THREAD_NUM; j++)
      threads[j].join();
    System.out.println("sync costs time: " + (System.currentTimeMillis() - begin));
  }
}