Java 线程控制（输出奇偶数）

两个线程，一个输出1，3，5，7......99；另一个输出2，4，6，8......100。

1.线程同步

 public class ST2 {
     int i = 0;

     public static void main(String[] args) {
         ST2 st1 = new ST2();
         new Thread(st1.new Inc()).start();
         new Thread(st1.new Dec()).start();
     }

     private synchronized void inc(){
         i++;
         try {
             Thread.currentThread().sleep(1000);
         } catch (InterruptedException e) {
             e.printStackTrace();
         }
         System.out.println(Thread.currentThread().getName()+" +++  "+i);
     }

     private synchronized void dec(){
         i--;
         try {
             Thread.currentThread().sleep(1000);
         } catch (InterruptedException e) {
             e.printStackTrace();
         }
         System.out.println(Thread.currentThread().getName()+" -----  "+i);
     }

     class Inc implements Runnable{
         @Override
         public void run() {
             while(true)
                 inc();
         }
     }

     class Dec implements Runnable{
         @Override
         public void run() {
             while(true)
                 dec();
         }
     }
 }

输出：

Thread-1 -----  -1
Thread-1 -----  -2
Thread-0 +++  -1
Thread-0 +++  0
Thread-0 +++  1
Thread-0 +++  2
Thread-1 -----  1
Thread-0 +++  2
Thread-1 -----  1
Thread-1 -----  0
Thread-1 -----  -1
Thread-1 -----  -2
Thread-0 +++  -1
Thread-0 +++  0
Thread-0 +++  1
Thread-1 -----  0
Thread-1 -----  -1
Thread-1 -----  -2
Thread-1 -----  -3
Thread-1 -----  -4
Thread-0 +++  -3
Thread-0 +++  -2
Thread-0 +++  -1
Thread-0 +++  0

从这里可以看出，线程随机执行。

2.控制线程执行顺序

     private synchronized void inc() throws Exception{
         b = true;
         notifyAll();
         i++;
         System.out.println(Thread.currentThread().getName()+" ++  "+i);

         Thread.currentThread().sleep(1000);

         while(b)
             wait();
     }

     private synchronized void dec() throws Exception {
         while(!b)
             wait();
         i++;
         System.out.println(Thread.currentThread().getName()+" ++++  "+i);

         Thread.currentThread().sleep(1000);

         b = false;
         notifyAll();
     }

输出：

Thread-0 ++  1
Thread-1 ++++  2
Thread-0 ++  3
Thread-1 ++++  4
Thread-0 ++  5
Thread-1 ++++  6
Thread-0 ++  7
Thread-1 ++++  8
Thread-0 ++  9
Thread-1 ++++  10
Thread-0 ++  11
Thread-1 ++++  12
Thread-0 ++  13
Thread-1 ++++  14
Thread-0 ++  15
Thread-1 ++++  16
Thread-0 ++  17
Thread-1 ++++  18
Thread-0 ++  19
Thread-1 ++++  20
Thread-0 ++  21

3.控制线程执行次数

 class Inc implements Runnable{
             @Override
             public void run() {
                     for(int j=0 ; j<50; j++){
                             try {
                                 inc();
                             } catch (Exception e) {
                                 e.printStackTrace();
                             }
                     }
             }
     }

     class Dec implements Runnable{
             @Override
             public void run() {
                 for(int j=0 ; j<50; j++){
                             try {
                                 dec();
                             } catch (Exception e) {
                                 e.printStackTrace();
                             }
                     }
             }
     }