LAB-14: Java Inner Class

Select File from top-level menu and select New Project.
Observe that the New Project dialog box appears.
Select Java under Categories section and Java Application under Projects section.
Click Next.

Under Name and Location pane, for the Project Name field, enter InnerClassExample. (Figure-1.10 below)
Click Finish.

Figure-1.10: Create a new NetBeans project

Observe that the InnerClassExample project node is created under Projects pane of the NetBeans IDE and IDE generated Main.java is displayed in the editor window of the IDE.

2. Modify the IDE generated Main.java as shown in Code-1.11 below.

package innerclassexample;

public class Main {

    public static void main(String[] args) {

        // Create an object instance of a class that contains
        // an inner class - we will call it outer class.
        OuterClass oc = new OuterClass();

        // Create an object instance of an inner class.
        OuterClass.InnerClass ic = oc.new InnerClass();

        // Display data from both outer class and inner class.
        System.out.println("Access data from outer class = " + oc.data);
        System.out.println("Access data2 from inner class = " + ic.data2);

        // Invoke a method from an inner class
        ic.method();
    }

}

Code-1.11: Main.java

3. Write OuterClass.java as shown in Code-1.12 below.

package innerclassdemo;

/**
*
* @author sang
*/
public class OuterClass {

    /** Creates a new instance of OuterClass */
    public OuterClass() {
    }

    // Define a variable in the outer class
    int data = 5;

    // Define an inner class
    class InnerClass {
        int data2 = 10;
        void method() {
            System.out.println("data from OuterClass = " + data);
            System.out.println("data2 from InnerClass = " + data2);
        }
    }

}

Code-1.12: OuterClass.java

3. Build and run the program

Right click InnerClassExample project node and select Run.
Observe the result in the Output window of the NetBeans IDE. (Figure-1.12 below)

Access data from outer class = 5
Access data2 from inner class = 10
data from OuterClass = 5
data2 from InnerClass = 10

Figure-1.13: Result

Summary

In this exercise, you have build and run Java applications that use an inner class.

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Homework

package innerclassexample;

public class InnerClassDemo {

    public static void main(String[] args) {

        // Create an object instance of a class that contains
        // an inner class - we will call it outer class.
        OuterClass oc = new OuterClass();

        // Create an object instance of an inner class.
        OuterClass.InnerClass ic = oc.new InnerClass();

        // Create an object instance of an inner class.
        OuterClass.InnerClass.InnerInnerClass iic = ic.new InnerInnerClass();

        // Display data from both outer class and inner class.
        System.out.println("Access data from outer class = " + oc.data);
        System.out.println("Access data2 from inner class = " + ic.data2);
        System.out.println("Access data3 from innerinner class = " + iic.data3);

        // Invoke a method from an inner class
        ic.method();
        iic.method2();
    }

}

Code-1.15: Modified InnerClassDemo.java

Java Inner Class

Exercises and homework

Exercise 1: Build and run Java applications that use inner class

(1.1) Build and run a simple application that uses an inner class

Summary

Homework