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Java Eclipse Tutorial – Part 7: Debugging Java Source Code
Last Updated on Thursday, 14 May 2015 Written by Chad Darby Saturday, 16 August 2014
In this video tutorial, I will show you how to use Eclipse to debug your source code. I will discuss the following topics:
- Setting breakpoints
- Starting the debugger
- Stepping through code
- Viewing variable
- Changing variable values
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|1||Installing the Eclipse IDE||03:18|
|2||Create a Java Application with Eclipse||03:44|
|3||Exploring the Eclipse User Interface||04:50|
|4.1||Searching and Navigating Source Code (part 1)||04:18|
|4.2||Searching and Navigating Source Code (part 2)||06:06|
|5||Generating Java Source Code||05:12|
|6.1||Refactoring Code - Extract Constants and Variables||04:13|
|6.2||Refactoring Code - Extract Methods, Rename Methods and Variables||04:19|
|7||Debugging Java Source Code||04:34|
|8||Adding JAR Files||05:17|
|9||Running JUnit Tests||05:08|
|12||Setting Eclipse Preferences||04:09|
Time – 00:00
Hi. This is Chad (shod) of luv2code.com.
Time – 00:05
Welcome back to another tutorial on Eclipse. In this video, you will learn how to use Eclipse to debug Java source code. I will cover the following topics, setting breakpoints, starting the debugger, stepping through a code, viewing variables, and changing variable values.
Time – 00:23
Okay. Let’s get started. We will learn how to use debugging with a sample program. I have a program that would generate a list of random students. The program will also display the students. I’ll run the program just so you can see the output. As you can see at the bottom, the program simply creates three students and displays the information to the screen.
Time – 00:45
Before we can debug the code, we must set a breakpoint. A breakpoint is the line of code the debug at during the debugging session. In the main method, let’s set a breakpoint on line 20. I’ll “right click”. I’ll say, “Toggle breakpoint.”
Time – 00:59
Now, let’ start the debugger. Right click the application and select “Debug As Java Application.” Eclipse will ask you if you want to use the debug perspective. Select “Yes” because this give us special views that can aid us in the debugging process.
Time – 01:15
Once the program starts running, it will stop at the breakpoint we set on line 20. At this point, the program executes this pause. We can inspect the variables, but there is nothing interesting up there yet.
Time – 01:30
At this point, what I want to do is simply step over a code. I’m going to use this item here on the toolbar, “Step Over.” I’ll step over the next line. I’ll step over for the loop. At this point, I actually want to move into this method, because there’s a method called “Create Random Student,” and I want to move into it and see the actual internals for it.
Time – 01:50
To step into the method, Create Random Student, I will use this toolbar option, “Step Into,” and I’ll select it. Now, this will actually take me into the Create Random Student method. At this level, I want to step over each one of these methods. I basically just want to execute this line of code.
Time – 02:07
The one thing I want to draw your attention to is a section up here at the top for the variable so you’re going to see new variables pop up with new values. I’ll step over again. That’s our temp first name. We get the last name index. We get the last name. We get our random age, and then we create a student object.
Time – 02:25
Note here that we have the student object created. I can expand the student object and I can actually get information about the various fields that are defined in it. This temp student that was created has the age of 33, first name was David and last name was Adams. This matches with the variables that were defined as I was stepping over the code.
Time – 02:46
Then, here, I’ll do one more step. This will return back to the call. At the result here, I’ll step over one more time. Then I have the student object that’s created. It also has the same data that was returned from that method.
Time – 02:59
Let’s walk through the loop one more time. I’ll just do a step over, and, now, I’ll do a step into. I will step over each one of these. I will get the temp first name. I’ll get a temp last name, and I’ll get an age.
Time – 03:16
What I’d like to do now is I want to actually change some values before I actually create the student object. I’ll choose first name here and I will “right click”. Instead of the name of Claire, I want to change the name to Daffy and hit “OK.” For last name, instead of Davis, I want to change this value to Duck and then hit “OK.” Now, we have a student Daffy Duck. Then we will continue with looping through the example. This will bring us back to this temp student we’ve created and, now, if I expand it, we can see that this student now has the value of Daffy Duck.
Time – 03:58
At this point, I don’t want to continue stepping to the code one line at a time. I’d like to simply resume running at normal execution speed. On my toolbar, I can move up and I could select “Resume.” Notice the output of the program. We have the three students. The second student is the one that we modified during the execution, and that’s Daffy Duck, last name, first name.
Time – 04:21
We were successful in debugging our Java Program with Eclipse. This wraps our video on debugging.
Time – 04:29
You learned how to use Eclipse to set breakpoints and debug a Java application. Please subscribe to our channel to view more videos on Eclipse and Java. Click the “Thumbs Up” to like our video. Also, visit our website, luv2code.com to download the Java source code used in this video.