How to Use a Custom Class in Another Class in Java

Struggling to reference one Java class from another within the same package? This guide helps you troubleshoot common errors and provides step-by-step instructions to resolve the issue.
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How to Use a Custom Class in Another Class in Java

If you're new to Java programming, you might have encountered some frustrating issues while trying to work with multiple classes in the same package. This guide will address a common problem: how to create an instance of one class within another class located in the same package. Let's break it down to help you understand what went wrong and how to fix it.

The Problem

When you try to reference a custom class inside another class, you might see an error in your console that states something like: cannot find symbol. This typically indicates that the Java compiler can't locate the class you are trying to instantiate. In this scenario, we have two classes in the same package: Stakeholders and ClientIndividual. The aim is to create an instance of ClientIndividual in the Stakeholders class.

Example Code Structure

Your file structure looks like this:

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Here are simplified versions of the code in each file.

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The Cause of the Error

The error arises not from your code itself but from a misconfiguration in your compilation process. When you are compiling your files, it’s important to ensure that you have set the correct working directory. If your command-line interface is set to the folder containing your package (like substitutiva), the Java compiler won't be able to find your ClientIndividual class when you attempt to create an instance of it.

Solution: Proper Compilation Steps

To resolve this issue, follow these simple steps:

Change the working directory: Navigate to the root folder where your packages reside. This should be the parent directory of substitutiva, not substitutiva itself.

Compile from the root: Use the command below to compile your class, making sure to specify the package path correctly:

[[See Video to Reveal this Text or Code Snippet]]

Run the compiled code: To run the Stakeholders class afterward, you can issue the command:

[[See Video to Reveal this Text or Code Snippet]]

Summary

Working with multiple classes in Java can be tricky, especially when it comes to compiling them correctly. If you encounter the cannot find symbol error, double-check that your compilation directory is set to the root of your package. Using the correct command will help the Java compiler find all necessary references.

By following the steps outlined in this guide, you should be able to successfully reference one class from another within the same package. Happy coding!