The Java debugger provides the ability to set breakpoints and watches, to step through code, to examine and modify variables, to examine classes and the callstack, to follow threads, and to run multiple sessions. The JPDA is the default debugger if you are running the Java 2 Platform, Standard Edition (J2SE), SDK 1.3.
For more information, see:
The Debug Environment
Starting a Debugging Session
Controlling Program Execution
Setting Breakpoints
Debugging Threads
Using the Call Stack
Examining Variables
Examining the Classes Loaded by the Program
Configuring the Debugger