What are the best practices for using nested classes in Java?

What are the best practices for using nested classes in Java?

When using nested classes in Java, consider the following best practices: 1. Use static nested classes for utility functions that don't require access to the outer class's instance. 2. Use inner classes when you need to access the outer class's instance variables. 3. Keep nested classes focused and cohesive to maintain readability. 4. Avoid deep nesting to prevent complexity.

Can you give an example of a static nested class?

Sure! Here's a simple example:

class OuterClass {
    static class StaticNestedClass {
        void display() {
            System.out.println("Inside static nested class.");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        OuterClass.StaticNestedClass nested = new OuterClass.StaticNestedClass();
        nested.display();
    }
}

What about inner classes? How do they differ?

Inner classes are associated with an instance of the outer class and can access its members. Here's an example:

class OuterClass {
    private String outerField = "Outer field";

    class InnerClass {
        void display() {
            System.out.println(outerField);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        OuterClass outer = new OuterClass();
        OuterClass.InnerClass inner = outer.new InnerClass();
        inner.display();
    }
}

Are there any performance considerations with nested classes?

Yes, using nested classes can have performance implications. Static nested classes do not hold a reference to the outer class, which can save memory. However, inner classes hold an implicit reference to the outer class, which can lead to increased memory usage if not managed properly.