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Watch and Variables in Eclipse

Introduction

Debugging is an essential part of software development. In Eclipse, the "Watch" feature allows developers to monitor the value of variables during runtime. This tutorial will guide you through the process of using watch expressions and understanding variables in Eclipse.

What are Variables?

A variable is a symbolic name associated with a value and whose associated value may be changed. Variables are a fundamental concept in programming, allowing for data storage and manipulation.

Example:
int age = 25;

This line of code declares a variable named age and assigns it the value 25.

Setting Up a Debugging Session

To use the watch feature, you first need to start a debugging session. Here’s how to do it:

  1. Open your Java project in Eclipse.
  2. Set a breakpoint in your code by double-clicking on the left margin next to the line number.
  3. Right-click on your project and select Debug As -> Java Application.

Using Watch Expressions

Once you hit a breakpoint during debugging, you can add watch expressions to inspect variable values.

  1. In the Debug perspective, locate the Expressions view.
  2. Right-click inside the Expressions view and select Add Watch Expression.
  3. Type the variable name you want to watch (e.g., age) and press Enter.
Example:

When you add age as a watch expression, you will see its value update in real-time as you step through your code.

Viewing Variable Values

As you continue to debug, the values of the watched variables will be displayed in the Expressions view. This allows you to observe how variable values change with each execution step.

Example:

If you have a loop that increments age, you will see the value of age increase with each iteration:

for(int i = 0; i < 5; i++) { age++; }

Removing Watch Expressions

If you no longer wish to watch a variable, you can easily remove it from the Expressions view:

  1. Right-click on the variable in the Expressions view.
  2. Select Remove to delete the watch expression.

Conclusion

The watch feature in Eclipse is a powerful tool for monitoring the state of variables during debugging sessions. By effectively using watch expressions, you can gain insights into the behavior of your code and identify issues more efficiently.

Experiment with different variables and watch expressions to become proficient in debugging with Eclipse.