What are the differences between nested classes and inner classes in Java?

What are the differences between nested classes and inner classes in Java?

In Java, a nested class is a class defined within another class. An inner class is a specific type of nested class that has access to the outer class's members, including private ones. Essentially, all inner classes are nested classes, but not all nested classes are inner classes.

Can you give me an example of each?

Sure! Here's an example of a nested class:

class Outer {
    static class Nested {
        void display() {
            System.out.println("This is a nested class.");
        }
    }
}

And an example of an inner class:

class Outer {
    class Inner {
        void display() {
            System.out.println("This is an inner class.");
        }
    }
}

What are the use cases for using inner classes?

Inner classes are useful when you want to logically group classes that will only be used in one place, and they can access the outer class's members directly. This can lead to more readable and maintainable code.

Are there any performance implications of using inner classes?

Yes, inner classes can have a slight performance overhead due to the implicit reference to the outer class. However, this is usually negligible unless you're creating many instances in performance-critical applications.