Question

I decompiled a source file and found some JVM instructions like JVM INSTR monitorenter and JVM INSTR monitorexit.
What does these mean?

public boolean isRunning()
    {
        this;
        JVM INSTR monitorenter ;
        Thread thread = _thread;
        boolean flag;
        if(thread != null)
            flag = true;
        else
            flag = false;
        this;
        JVM INSTR monitorexit ;
        return flag;
        Exception exception;
        exception;
        throw exception;
    }

Also what does Exception exception; , exception; and throw exception; mean?

Answer 1

monitorenter and monitorexit are documented in the JVM specification, along with all the other bytecode instructions. Basically they’re used to implement synchronized blocks and methods.

It sounds like your decompiler isn’t terribly good, if it isn’t able to come up with appropriate Java here… we can’t tell what the Exception part is about when basically it’s broken decompiler output. It may well correspond to something like:

catch(Exception exception)
{
    throw exception;
}

… but basically I’d find a different decompiler. (Why do you need a decompiler anyway?)