Compile Error : cannot find symbol constructor Thread(Runnable)

Hi,

Would you give me some adivce to solve this compiling error?
Thread class has a constructor which has argument Runnable class.
I can't understand why this happen.

=================================================================
RunnableTest.java:21: cannot find symbol
symbol : constructor Thread(RunnableTest)
location: class java.lang.Thread
new Thread(thread50).start();
^
RunnableTest.java:22: cannot find symbol
symbol : constructor Thread(RunnableTest)
location: class java.lang.Thread
new Thread(thread100).start();
^
2 errors
======================================================
/* RunnableTest.java */
import java.io.*;
class RunnableTest implements Runnable {
long delay;
String message;
RunnableTest(String message, long delay) {
this.message = message;
this.delay = delay;
}
public void run() {
try {
while(true) {
System.out.print(message+ " ");
Thread.sleep(delay);
}
} catch(InterruptedException e){ return; }
}
public static void main(String[] args) {
RunnableTest thread50 = new RunnableTest("t50", 50);
RunnableTest thread100 = new RunnableTest("t100", 100);
new Thread(thread50).start();
new Thread(thread100).start();
}
}

Compiled fine on my system without any errors. The code seems fine.

That's strange. It compiles fine for me. Are you sure you don't have a second copy of RunnableTest.java in your working directory, one that doesn't implement the Runnable interface?

It seems it's my computer problem. I tried on other PC and it works.

I don't know why but only calling java.lang.Thread costructor make compiling error happen.
Anyone knowing about this?

Most likely in your experimentation you created your own class named "Thread" or interface named "Runnable", and either the *.java or *.class files are still around on that machine. Use the Windows "Find File" feature to find Thread.java, Thread.class, Runnable.java and/or Runnable.class, and delete any ones you find that you may have created yourself.

I found there was Runnable.class in my classpath directory.
After deleting that file, it works.

Thank you , Ernest and all who replied.