Nested Classes

Nested Class:

• A class inside another class is called Nested class
• Modifiers of nested class is private, protected, static, abstract, final, public and default
• It is three types Member Inner class, Local Inner class and Anonymous Inner class

Example 1: Create a program that explains static nested class inside another outer class?

package com.java.nested;

public class StaticNestedClass {
    static int id;
    
    void echo(){
        id = 40;
        System.out.println("Outer class non-static method called by StaticInner class by Object Outer class StaticNestedClass echo() and Id = " + id);
    }
    
    static void print(){
        id = 20;
        System.out.println("Outer class static method called by StaticInner class directrectly print() and Id = " + id);
    }
    static class StaticInner{
        static void show(){
            id = 10;
            System.out.println("Inner class static method show() method can be called by Outer class throgh StaticNestedClass.StaticInner.show() and Id = " + id);
            print();
        }
        void display(){
            id = 30;
            System.out.println("Inner class non-static method display() cab be called by Outer class throght object of StaticInner class and Id = " + id);
            StaticNestedClass outer = new StaticNestedClass();
            outer.echo();
        }
    }
    public static void main(String[] args) {
        StaticNestedClass.StaticInner.show();

        StaticNestedClass.StaticInner inner = new StaticInner();
        inner.display();

    }
}

Output:
Inner class static method show() method can be called by Outer class throgh StaticNestedClass.StaticInner.show() and Id = 10
Outer class static method called by StaticInner class directrectly print() and Id = 20
Inner class non-static method display() cab be called by Outer class throght object of StaticInner class and Id = 30
Outer class non-static method called by StaticInner class by Object Outer class StaticNestedClass echo() and Id = 40

Example 2: Create a program that explains non-static Local Inner class inside another outer class?

package com.java.nested;

public class NonStaticOuterMemberClass {
    int id;
    void display(){
        id = 10;
        System.out.println("Outer class non-static method display() cab be called by Outer class throght object of NonStaticOuterMemberClass and Id = " + id);
        class LocalInnerClass{
            void print(){
                id = 20;
                System.out.println("Inner class non-static method print() called by NonStaticOuterMemberClass method display() by object of LocalInnerClass and Id = " + id);
            }
        }
        LocalInnerClass localInner = new LocalInnerClass();
        localInner.print();
    }
    public static void main(String[] args) {
        NonStaticOuterMemberClass outer = new NonStaticOuterMemberClass();
        outer.display();
    }
}

Output:
Outer class non-static method display() cab be called by Outer class throght object of NonStaticOuterMemberClass and Id = 10
Inner class non-static method print() called by NonStaticOuterMemberClass method display() by object of LocalInnerClass and Id = 20

Example 3: Create a program that explains non-static Member Inner class inside another outer class?

package com.java.nested;

public class NonStaticOuterClass {
    int id;
    class MemberInnerClass{
        void print(){
            id = 20;
            System.out.println("Inner class non-static method print() called by NonStaticLocalInnerClass method display() by object of MemberInnerClass and Id = " + id);
        }
    }
    void display(){
        id = 10;
        System.out.println("Outer class non-static method display() can be called by Outer class throght object of NonStaticLocalInnerClass and Id = " + id);
        
        MemberInnerClass localInner = new MemberInnerClass();
        localInner.print();
    }
    public static void main(String[] args) {
        NonStaticOuterClass outer = new NonStaticOuterClass();
        outer.display();
    }
}

Output:
Outer class non-static method display() can be called by Outer class throght object of NonStaticLocalInnerClass and Id = 10
Inner class non-static method print() called by NonStaticLocalInnerClass method display() by object of MemberInnerClass and Id = 20