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Discover how to handle `Jshell` not allowing generic types in IntelliJ IDEA with an easy workaround!
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This video is based on the question https://stackoverflow.com/q/62367579/ asked by the user 'Need Help' ( https://stackoverflow.com/u/13741014/ ) and on the answer https://stackoverflow.com/a/62367608/ provided by the user 'Aniket Sahrawat' ( https://stackoverflow.com/u/6099347/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Jshell Generic Types Problem in IntelliJ IDEA

If you've recently started using Jshell in the IntelliJ IDEA Community Edition and encountered issues with generic types, you're not alone. Many new users feel frustrated when they write code that should function correctly, only to be met with error messages. In this guide, we will dive into the problem and provide a solution to help you work effectively with generics in Jshell.

The Encountered Issue

You may have noticed that while your code works perfectly in Jshell, it doesn't do so in IntelliJ. For example, when attempting to create a list of strings like this:

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

You might encounter the error message: "Expression expected." The root of the problem lies in IntelliJ’s handling of auto-complete features when using generic types, making it a hassle to work with them directly in your scripts.

Solution: Using an Anonymous Class

While it may seem limiting, there's a neat workaround you can implement by utilizing an anonymous class. This technique helps to successfully run your desired code without having to resort to "raw types". Here's how you can do it:

Step-by-Step Implementation

Define an Anonymous Class: Create a new instance of Object and define a method inside it.

Include Your Code: Place your list declaration and print statement inside this method.

Invoke the Method: Finally, call that method to execute your code.

Here’s the code snippet demonstrating this workaround:

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

Why This Works

The anonymous class encapsulates the logic and allows the use of generics without running into issues with IntelliJ's parsing of the script. By creating a temporary object and method, you're effectively sidestepping the limitations imposed by the IDE on a top-level declaration.

Conclusion

Dealing with Jshell in IntelliJ IDEA, especially with generic types, can be somewhat tricky at first. However, by using the above approach with an anonymous class, you can easily overcome the limitations and write effective, type-safe code. If you continue to face challenges or have additional questions about working with generics, feel free to seek further clarification or explore additional resources.

Whether you're just starting out or you've matured in your Java journey, understanding these nuances can greatly enhance your coding experience in IntelliJ IDEA. Happy coding!