How to call inner class method from static, non static method and outside of outer class

Calling Regular inner class methods in Java

In this article, we learn about 3 ways to access inner class code or methods :

1. Call inner class method from Static method | How to instantiate non static inner class within a static method?
   
2. Call inner class method from non static method of outer class
3. Call inner class method from outside of outer class

So lets see one by one with code.

1. Calling inner class method from Static method | Instantiate non static inner class within a static method?

For instantiate inner class first we must have object of outer class. after that we can create object of inner class using outer class reference.

class OuterClass {

    class InnerClass {
        public void innerClassMethod() {
            System.out.println("Non Static Inner class");
        }
    }
    
    public static void main(String[] args) {
       OuterClass outerObj = new OuterClass();
       OuterClass.InnerClass innerObj = outerObj.new InnerClass();
       innerObj.innerClassMethod();
    }
}

Output :

Non Static Inner class

We can also write main method code in 1 line as following :

new OuterClass().new InnerClass().innerClassMethod();

So first we created object of OuterClass, then created object of InnerClass using OuterClass reference. And then we can access InnerClass non static method.

2. Calling inner class method from non static method of outer class

class OuterClass {

    class InnerClass {
        public void innerClassMethod() {
            System.out.println("Non Static Inner class");
        }
    }
    
    public void outerClassMethod() {
        System.out.println("Calling inner class Method from Non Static Outer class ...");
        InnerClass obj = new InnerClass();
        obj.innerClassMethod();
    }
    
    public static void main(String[] args) {
        OuterClass outerObj = new OuterClass();
        outerObj.outerClassMethod();
    }
}

Output :

Calling inner class Method from Non Static Outer class ...
Non Static Inner class

• We created non static method in OuterClass named outerClassMethod().
• In that we are creating object of InnerClass and calling inner class method named innerClassMethod(). 
  

3. Calling inner class method from outside of outer class  

class OuterClass {

    class InnerClass {
        public void innerClassMethod() {
            System.out.println("Non Static Inner class");
        }
    }
    
}

class Solution {
    public static void main(String[] args) {
        OuterClass outerObj = new OuterClass();
        OuterClass.InnerClass innerObj = outerObj.new InnerClass();
        innerObj.innerClassMethod();
    }
}

Output :

Non Static Inner class

It is same as calling inner class method from outer class static method, but here we are just calling inner class method from another class that is outside of outer class.

 

Happy Learning, Happy Coding...