5.3. Starting a Debugging Session
Problem
Your code isn’t running as you want it to, and it’s time to debug.
Solution
Start a new debugging session with the items in the Run menu. Then use the various debugging options, such as single-stepping, setting breakpoints, and more.
Discussion
Say you want your code to display this output:
3... 2... 1... Houston, we have liftoff.
Your first attempt at the code might look like that shown in Example 5-3, in the class DebugClass
in
an application named DebugApp
.
Example 5-3. The DebugApp example
package org.cookbook.ch05; public class DebugClass { public static void main(String[] args) { for(int loopIndex = 3; loopIndex > 0; loopIndex--) { System.out.println(loopIndex + "..."); if(loopIndex == 0) { System.out.println("Houston, we have liftoff."); } } } }
Unfortunately, the code in Example 5-3 gives you this result:
3... 2... 1...
It’s time to debug. To start a debugging session, use one of the following items in the Run menu:
- Run→ Debug History
Enables you to select a recently run project to debug
- Run→ Debug As
Enables you to select the type of session to run (Java Applet, Java Applications, JUnit Test, or Run-time Workbench) from a submenu
- Run→ Debug
Enables you to set the launch configuration for a debugging session
To start debugging the code in DebugApp
, select
Run→ Debug As→ Java Application, which opens and
runs your code in the Debug perspective, as shown in Figure 5-8.
Figure 5-8. First attempt at debugging
Take a look at the Debug perspective in Figure ...