How to Create an Array of Objects in Java with OOP Principles

Learn how to effectively create an array of objects in Java, combining different classes in an easy-to-understand format.
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Creating an Array of Objects in Java: A Step-by-Step Guide

In the world of Object-Oriented Programming (OOP), managing collections of objects can be a common yet tricky task, especially when you want to work with multiple classes. A typical scenario arises when you need to create an array of objects where some objects belong to one class, and others belong to a different class. In this guide, we will explore a real-world problem that many Java developers face and provide a clear solution to implementing an array with multiple object types.

The Problem

A developer faced a situation where they had created two classes, Pupil and Tutor, each with its constructors:

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

In their Main class, they instantiated three Pupil objects and one Tutor object:

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

However, when they tried to create a fourth class called Groups, intending to group these objects into an array, they encountered a “cannot resolve any symbols” error.

The Solution

Understanding Java Arrays

In Java, arrays have a specific limitation: they can only contain objects of the same type. Consequently, if you try to create an array that mixes Pupil and Tutor, the compiler gets confused and raises an error.

Step-by-Step Approach

Here's how to address this issue effectively:

Use the Object Class: Since both Pupil and Tutor are different classes, you can store them in an array that holds Object types.

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

By using Object[], you are telling the Java compiler that you want an array that can hold any object type. This is possible because all classes in Java inherit from the Object class.

Implementing the Groups Class: The new Groups class should then look like this:

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

Utilizing instanceof for Type Checking: Since the array holds different types of objects, it's essential to check the type of each object when accessing its properties. You can use the instanceof operator, as shown in the loop above, to safely cast the object to its respective type before accessing its properties.

Conclusion

Creating an array of objects from different classes can initially seem daunting, but with a clear understanding of Java arrays and the principles of OOP, it becomes manageable. By utilizing the Object class, you can circumvent type restrictions and store diverse objects within a single array. This approach not only resolves the error but also allows you to efficiently manage and utilize an array of heterogeneous objects.

With this simple yet effective method, you can effectively group different types of objects in Java while practicing good programming principles. Happy coding!