Скачать или смотреть How to Access a static ArrayList from Another Class in Java

Learn how to effectively access a `static ArrayList` from one class in Java to another, using a simple getter method. Perfect for beginners!
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This video is based on the question https://stackoverflow.com/q/63531740/ asked by the user 'Dean' ( https://stackoverflow.com/u/14140348/ ) and on the answer https://stackoverflow.com/a/63531770/ provided by the user 'Mureinik' ( https://stackoverflow.com/u/2422776/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Accessing a static ArrayList from Another Class in Java

In Java programming, it's not uncommon for developers to encounter situations where they need to share data between different classes. One common data structure used for this purpose is the ArrayList. However, issues can arise when trying to access a static ArrayList from another class. In this guide, we'll explore a typical problem and provide a clear solution.

The Problem

Imagine you have a static ArrayList defined in a main class, let's call it CityMenuCreate. You've created a getter method in this class to retrieve the ArrayList. You then attempt to access this static list from a second class, but you hit a roadblock. Despite calling the getter method correctly, you encounter a compiler error when trying to use the list in a for loop.

Here's a quick look at the relevant code:

The Getter Method in CityMenuCreate

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Attempting to Access the List in Another Class

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The problem is in the line where you try to access cityList.size().

The Solution

The key issue here is that when you call CityMenuCreate.getCityList(), you're not storing the returned ArrayList in a variable. Instead, you're trying to access the list directly, which leads to a compilation error.

Step 1: Store the Returned Value

You need to capture the list returned by the method. Here’s how you can do this:

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In this example:

cityList now holds the reference to the ArrayList returned by the getter method, allowing you to use cityList.size() without any issues.

Step 2: Use the Returned Value Directly

Alternatively, you can also use the returned value directly within the loop, as shown below:

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In this case, you are calling the getter method each time the loop checks the condition. This is perfectly valid, but it’s usually more efficient to store the result in a variable if the list is large or if you need to access it multiple times.

Conclusion

Accessing a static ArrayList from another class in Java can be straightforward once you remember to handle the return value correctly. Whether you choose to store the list in a variable or use it directly in your loop, ensuring you're working with the returned object will solve the problem you're facing.

By following these steps, you can effectively share an ArrayList between classes in Java and focus on building more complex functionalities without getting bogged down by simple errors.

If you have any comments or questions, feel free to share them below!