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Learn how to resolve issues with custom methods in Java classes that implement interfaces like Runnable, including practical examples and solutions.
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This video is based on the question https://stackoverflow.com/q/68635814/ asked by the user 'user1406186' ( https://stackoverflow.com/u/1406186/ ) and on the answer https://stackoverflow.com/a/68635888/ provided by the user 'David' ( https://stackoverflow.com/u/328193/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Properly Use Setter Methods in a Class That Implements Runnable in Java

Java's object-oriented capabilities allow for the implementation of interfaces in a tidy and efficient manner. However, it can sometimes be tricky to use custom methods in classes that implement these interfaces. In this post, we will explore a specific question regarding the use of setter methods in a class that implements the Runnable interface. Let's dive into the problem and its solution.

The Problem: Cannot Resolve Method Error

In a given piece of code, the user created a class called SignalRunnable which implements the Runnable interface and contains a custom setter method called setS. The user faced an issue when trying to use this setter method on an instance of the Runnable interface, leading to a "cannot resolve method" error. The relevant code snippets from their attempt look like this:

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

And the usage attempt:

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

The crux of the problem lies in the fact that the variable runnable is declared as type Runnable, which does not have access to the setS method.

The Solution: Using the Correct Type

To resolve the issue, you need to change the type of the runnable variable from Runnable to your concrete class SignalRunnable. This way, you can access the custom method setS without encountering the resolution error. Here is the corrected code:

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

Why This Works

Type Compatibility: By declaring runnable as SignalRunnable, you gain access to all of its methods, including your custom setter setS.

Functionality Retained: You can still use SignalRunnable wherever a Runnable is expected, such as adding it to collections of Runnable or passing it to methods that require a Runnable. This means you won't lose the functionality that comes with implementing the interface.

Final Remarks

The key takeaway here is understanding the relationship between interfaces and classes in Java. Custom methods belong to classes, and if you want to use them, you must reference the class type rather than the interface type. By ensuring you have the correct variable type, you can leverage the full capabilities of your classes without running into method resolution issues.

With this understanding, you can confidently implement classes that utilize setter methods even while implementing interfaces like Runnable. Happy coding!