The class file for a new Thread and the class file for main are the same

Question

I have a program called Main.java, shown as below. After compilation of this program, there will be two .class file: Main.class and Main$1.class. My problem is the two .class files are exactly the same.

Anyone knows what is wrong?

I wan to instrument some codes in the run() method of the new thread, but I cannot find the instructions of codes in the run() method of a new thread.

public class Main{
    public static void main(String...args){
         Thread t=new Thread(){
         @Override
             public void run(){
             System.out.println("xxxx");
             }
         };
    t.start();
    }
}

My money would be on you not comparing the two class files correctly. — Andy Turner, Oct 09 '16 at 19:23
No idea what you are asking. What do you mean by those two class files are the same? They cant. One is for the outer public Main class; and the other one is for an inner, anonymous class. Two completely different things! — GhostCat, Oct 09 '16 at 19:23

Andy Turner · Answer 1 · 2016-10-10T06:38:37.203

My money would be on you not comparing the two class files correctly. I'd bet that you're writing something like this in your bash-like prompt:

md5sum Main.class Main$1.class

(or some checksumming tool other than md5sum)

This is actually substituting the variable called 1 in the string - unless you've got that variable defined, that variable is empty, so that is expanding to:

md5sum Main.class Main.class

which will show as the same file contents.

Try single-quoting the second string:

md5sum Main.class 'Main$1.class'

The class file for a new Thread and the class file for main are the same

1 Answers1