THE UNIVERSITY OF WESTERN AUSTRALIA

Department of Computer Science

230.304 CONCURRENT PROGRAMMING

Laboratory Sheet 4 (for laboratories during week 6)

The purpose of this laboratory is to :

• Use the jdb to debug multithreaded java programs.
• Write Java programs for mutual exclusion using semaphores, and

The java debugger

You may have already used the java debugger. It is a good tool for debugging multithreaded java programs and some of you may find it useful for debugging your project.

To use jdb, you have to compile a java program using the -g option. We will use the program Example1.java for experimenting with jdb.

Compile the program using :

javac -g Example1.java

Now the compiler will include additional information in the class file. To invoke the debugger, you have to use :

jdb Example1

Here is a list of options that you can use in the debugger. You may see all these options by invoking the help command in the debugger.

Here is a file where I have executed different commands in jdb. The lines after // are my comments.

Tasks

• Try to use the jdb
• Try to implement the Wait() and Signal() operations on a semaphore using wait() and notify() methods of Java. Write a class Semaphore which includes these two methods. Here is a skeleton file for the semaphore class. Write solution for the mutual exclusion problem using your class for semaphores. Test your solution for two and more threads. You may use the file Attempts.java supplied in one of the previous labs.