程序主体如下：
package test;
public class ThreadRangbu {
public static void main(String[] args) throws Exception {
Thread01 thread01 = new Thread01();
thread01.start();
for (int i =0; i<5;i++){
try{
Thread.currentThread().sleep(100);
System.out.println(Thread.currentThread().getName() +" is executing!");
//System.out.println("i="+i);
} catch (Exception e){
}
}
}
}
class Thread01 extends Thread{
public void run(){
for (int i =0; i<5;i++){
try{
Thread.currentThread().sleep(100);
}catch(Exception e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() +" is running!");
//System.out.println("i="+i);
if (i%2==0){
Thread.yield();
System.out.println("Terminate current sub-thread.");
}
}
}
}
教科书上的结论说程序运行结果应该是是：
main is executing!
Thread-0 is running!
Thread-0 is running!
main is executing!
Terminate current sub-thread.
main is executing!
Thread-0 is running!
main is executing!
Thread-0 is running!
Terminate current sub-thread.
而程序实际运行的结果如下：
Thread-0 is running!
main is executing!
Terminate current sub-thread.
Thread-0 is running!
main is executing!
Thread-0 is running!
main is executing!
Terminate current sub-thread.
main is executing!
Thread-0 is running!
Thread-0 is running!
main is executing!
Terminate current sub-thread.
疑问一： 究竟哪个结果才是正确的？
当红色字体部分取消注释时，结果如下：
main is executing!
Thread-0 is running!
i=0
Terminate current sub-thread.
main is executing!
Thread-0 is running!
i=1
main is executing!
Thread-0 is running!
i=2
Terminate current sub-thread.
main is executing!
Thread-0 is running!
i=3
main is executing!
Thread-0 is running!
i=4
Terminate current sub-thread.
疑问二：为什么会产生这个变化？
当红色和蓝色字体都取消注释时，结果如下：
Thread-0 is running!
i=0
main is executing!
i=0
Terminate current sub-thread.
main is executing!
i=1
Thread-0 is running!
i=1
Thread-0 is running!
i=2
main is executing!
i=2
Terminate current sub-thread.
Thread-0 is running!
i=3
main is executing!
i=3
Thread-0 is running!
i=4
main is executing!
i=4
Terminate current sub-thread.
疑问三：同疑问二，为什么取消注释又有了这样的变化？
总的疑问：对java中线程的执行处理次序不是很明白。以原程序为例（注释两行的程序）我的理解如下：
主方法中“Thread01 thread01 = new Thread01();thread01.start();”创建新的实例thread01,并且调用thread01中的方法run()，其中因为有“System.out.println(Thread.currentThread().getName() +" is running!");”语句，所以程序第一行应该是Thread-0 is running!
此时i=0，故返回主线程，因“System.out.println(Thread.currentThread().getName() +" is executing!");”语句，得到main is executing!
然后返回执行run()得到“Terminate current sub-thread.”结果。
之后i递增，返回main中运行程序，得到与书中不符的结果。
请问高手，我的理解是否正确？ 如果有错误，哪里理解存在问题？ 请帮我指点一下，谢谢。
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线程的执行顺序是随机的，不确定的
可以参照《操作系统》中有关进程调度的内容
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