How to call inner class from outer class in Java?

How to call inner class from outer class in Java?

I'm glad you're asking a question that's not related to grandma!

In Java, an inner class is a class defined within another class. To call an inner class from the outer class, you can use one of the following methods:

For example:

public class Outer {
public class Inner {
public void doSomething() {
System.out.println("Inner class method called");
}
}
public static void main(String[] args) {
Outer.Inner inner = new Outer().new Inner();
inner.doSomething(); // Outputs: "Inner class method called"
}
}

In this example, we create an instance of the Inner class using the new keyword and then call its doSomething() method.

For example:

public class Outer {
public static class Inner {
public static void doSomething() {
System.out.println("Inner class method called");
}
}
public static void main(String[] args) {
Inner.doSomething(); // Outputs: "Inner class method called"
}
}

In this example, we define a static doSomething() method in the Inner class that can be called directly from the outer class.

For example:

public class Outer {
public interface Inner {
void doSomething();
}
public static void main(String[] args) {
Inner inner = new Outer.Inner() { public void doSomething() { System.out.println("Inner class method called"); } };
inner.doSomething(); // Outputs: "Inner class method called"
}
}

In this example, we define an interface Inner in the outer class and then create a lambda expression that implements this interface. We can then call the doSomething() method on this lambda expression.

For example:

public class Outer {
public class Inner {
public void doSomething() {
System.out.println("Inner class method called");
}
}
public static void main(String[] args) {
new Outer.Inner() { public void doSomething() { System.out.println("Inner class method called"); } }.doSomething(); // Outputs: "Inner class method called"
}
}

In this example, we create an anonymous instance of the Inner class using an anonymous inner class and then call its doSomething() method.

These are some ways to call an inner class from the outer class in Java. Each method has its own advantages and disadvantages, and you should choose the one that best fits your needs.

Is it good practice to use inner class in Java?

The age-old debate about the use of inner classes in Java!

In Java, an inner class is a non-static nested class that has access to the members (methods and variables) of its outer class. Inner classes can be used as utility classes, providing functionality that's specific to their enclosing class. So, is it good practice to use inner classes in Java? Let's dive into the pros and cons.

Pros:

Cons:

Best practices:

In conclusion, using inner classes in Java can be a good practice when:

However, it's essential to weigh these benefits against the potential drawbacks. Inner classes are not a replacement for proper design principles and encapsulation. When in doubt, consider alternative approaches, such as using static utility classes or decomposing complex logic into separate, reusable components.