What Do Angle Brackets (<>) Indicate in Java Generics?

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Understanding Angle Brackets (<>) in Java

In Java, angle brackets (<>) denote generics. Generics allow you to create classes, methods, and interfaces that can work with different data types.

Class Definition Syntax

When defining a generic class, you specify a type parameter, such as , within the class declaration. For example:

public class Pool<T> {

    ...
}

The type parameter indicates that you can create an instance of this class with a specific data type. For instance, you can create:

Pool<String> pool = new Pool<>();

Type Parameters in Interfaces and Methods

You can also use type parameters in interfaces and methods. For example:

public interface PoolFactory<T> {

    T createObject();
}

In this interface, the type parameter specifies that the createObject() method must return an object of type T.

ArrayList

The ArrayList class is a generic container that can store objects of the specified type T. This means you can create an ArrayList that holds integers (ArrayList), strings (ArrayList), or any other data type.

Example

Let's consider your example:

public class Pool<T> {

    private ArrayList<T> freeObjects;

    ...
}

In this example, the Pool class is generic, and its freeObjects field is an ArrayList that holds elements of type T. This means you can create a Pool for objects of any data type.

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