（线程问题）各位高手为什么这个程序能编译不能运行啊？

[t427795737]

import java.io.*;

class StringRunnable implements Runnable
{
public static String str;
public StringRunnable()
{
System.out.println("StringRunnable");
}

public void run()
{
try
{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
str = in.readLine();
System.out.println(str);
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
}
}

public class StringThread extends Thread
{
public StringThread()
{
System.out.println("StringThread");
}

public void run()
{
System.out.println("The length of string is: " + StringRunnable.str.length());
}

public static void main(String[] args)
{
Thread thread1 = new Thread(new StringRunnable());
thread1.setPriority(Thread.MAX_PRIORITY);
thread1.start();
Thread thread2 = new StringThread();
thread2.start();
}
}

[qybao]

在你的另一个帖子里回答了
StringRunnable.str没有初始化，还是null, thread2走到System.out.println("The length of string is: " + StringRunnable.str.length());
时会出异常

thread1的优先级高并不代表threa1不执行完thread2就不执行，多以当thread1执行到str = in.readLine(); 时，如果用户不能及时响应输入数据，thread1就会一直堵塞，等待用户输入，而此时thread2就有可能执行，这样thread2走到System.out.println("The length of string is: " + StringRunnable.str.length()); 时，由于StringRunnable.str还是null，就造成thread2异常终了了

如果要保证顺序执行，可以不用设优先级，用jion就可以了
Thread thread1 = new Thread(new StringRunnable());
//thread1.setPriority(Thread.MAX_PRIORITY);
thread1.start();
thread1.jion(); //
Thread thread2 = new StringThread();
thread2.start();