![Page 3Classification: Restricted
Inner Classes (Non-static Nested Classes)
class Outer_Demo {
int num;
// inner class
private class Inner_Demo {
public void print() {
System.out.println("This is an inner class");
}
}
// Accessing he inner class from the method within
void display_Inner() {
Inner_Demo inner = new Inner_Demo();
inner.print();
}
}
public class My_class {
public static void main(String args[]) {
// Instantiating the outer class
Outer_Demo outer = new Outer_Demo();
// Accessing the display_Inner() method.
outer.display_Inner();
}
}](https://image.slidesharecdn.com/session21-innerclasses-slides-180607181137/85/Session-21-Inner-Classes-4-320.jpg)
![Page 4Classification: Restricted
Example: Accessing private members using Inner Class
class Outer_Demo {
// private variable of the outer class
private int num = 175;
// inner class
public class Inner_Demo {
public int getNum() {
System.out.println("This is the getnum method of the inner class");
return num;
}
}
}
public class My_class2 {
public static void main(String args[]) {
// Instantiating the outer class
Outer_Demo outer = new Outer_Demo();
// Instantiating the inner class
Outer_Demo.Inner_Demo inner = outer.new Inner_Demo();
System.out.println(inner.getNum());
}
}](https://image.slidesharecdn.com/session21-innerclasses-slides-180607181137/85/Session-21-Inner-Classes-5-320.jpg)
![Page 5Classification: Restricted
Method-local Inner Class
public class Outerclass {
// instance method of the outer class
void my_Method() {
int num = 23;
// method-local inner class
class MethodInner_Demo {
public void print() {
System.out.println("This is method inner class "+num);
}
} // end of inner class
// Accessing the inner class
MethodInner_Demo inner = new MethodInner_Demo();
inner.print();
}
public static void main(String args[]) {
Outerclass outer = new Outerclass();
outer.my_Method();
}
}](https://image.slidesharecdn.com/session21-innerclasses-slides-180607181137/85/Session-21-Inner-Classes-6-320.jpg)
![Page 6Classification: Restricted
Anonymous Inner Class
abstract class AnonymousInner {
public abstract void mymethod();
}
public class Outer_class {
public static void main(String args[]) {
AnonymousInner inner = new AnonymousInner() {
public void mymethod() {
System.out.println("This is an example of anonymous inner class");
}
};
inner.mymethod();
}
}](https://image.slidesharecdn.com/session21-innerclasses-slides-180607181137/85/Session-21-Inner-Classes-7-320.jpg)
![Page 7Classification: Restricted
Example: Anonymous Inner Class as Argument
// interface
interface Message {
String greet();
}
public class My_class {
// method which accepts the object of interface Message
public void displayMessage(Message m) {
System.out.println(m.greet() +
", This is an example of anonymous inner class as an argument");
}
public static void main(String args[]) {
// Instantiating the class
My_class obj = new My_class();
// Passing an anonymous inner class as an argument
obj.displayMessage(new Message() {
public String greet() {
return "Hello";
}
});
}
}](https://image.slidesharecdn.com/session21-innerclasses-slides-180607181137/85/Session-21-Inner-Classes-8-320.jpg)
![Page 8Classification: Restricted
Static Nested Class
public class Outer {
static class Nested_Demo {
public void my_method() {
System.out.println("This is my nested class");
}
}
public static void main(String args[]) {
Outer.Nested_Demo nested = new Outer.Nested_Demo();
nested.my_method();
}
}](https://image.slidesharecdn.com/session21-innerclasses-slides-180607181137/85/Session-21-Inner-Classes-9-320.jpg)
Session 21 - Inner Classes
- 1. Java & JEE Training Session 21 – Inner Classes
- 2. Page 1Classification: Restricted Agenda • Inner Classes • Method-local Inner Class • Anonymous Inner Class • Static Nested Inner Class
- 3. Page 2Classification: Restricted Inner Classes
- 4. Page 3Classification: Restricted Inner Classes (Non-static Nested Classes) class Outer_Demo { int num; // inner class private class Inner_Demo { public void print() { System.out.println("This is an inner class"); } } // Accessing he inner class from the method within void display_Inner() { Inner_Demo inner = new Inner_Demo(); inner.print(); } } public class My_class { public static void main(String args[]) { // Instantiating the outer class Outer_Demo outer = new Outer_Demo(); // Accessing the display_Inner() method. outer.display_Inner(); } }
- 5. Page 4Classification: Restricted Example: Accessing private members using Inner Class class Outer_Demo { // private variable of the outer class private int num = 175; // inner class public class Inner_Demo { public int getNum() { System.out.println("This is the getnum method of the inner class"); return num; } } } public class My_class2 { public static void main(String args[]) { // Instantiating the outer class Outer_Demo outer = new Outer_Demo(); // Instantiating the inner class Outer_Demo.Inner_Demo inner = outer.new Inner_Demo(); System.out.println(inner.getNum()); } }
- 6. Page 5Classification: Restricted Method-local Inner Class public class Outerclass { // instance method of the outer class void my_Method() { int num = 23; // method-local inner class class MethodInner_Demo { public void print() { System.out.println("This is method inner class "+num); } } // end of inner class // Accessing the inner class MethodInner_Demo inner = new MethodInner_Demo(); inner.print(); } public static void main(String args[]) { Outerclass outer = new Outerclass(); outer.my_Method(); } }
- 7. Page 6Classification: Restricted Anonymous Inner Class abstract class AnonymousInner { public abstract void mymethod(); } public class Outer_class { public static void main(String args[]) { AnonymousInner inner = new AnonymousInner() { public void mymethod() { System.out.println("This is an example of anonymous inner class"); } }; inner.mymethod(); } }
- 8. Page 7Classification: Restricted Example: Anonymous Inner Class as Argument // interface interface Message { String greet(); } public class My_class { // method which accepts the object of interface Message public void displayMessage(Message m) { System.out.println(m.greet() + ", This is an example of anonymous inner class as an argument"); } public static void main(String args[]) { // Instantiating the class My_class obj = new My_class(); // Passing an anonymous inner class as an argument obj.displayMessage(new Message() { public String greet() { return "Hello"; } }); } }
- 9. Page 8Classification: Restricted Static Nested Class public class Outer { static class Nested_Demo { public void my_method() { System.out.println("This is my nested class"); } } public static void main(String args[]) { Outer.Nested_Demo nested = new Outer.Nested_Demo(); nested.my_method(); } }
- 10. Page 9Classification: Restricted Why use Nested classes? • It is a way of logically grouping classes that are only used in one place. • It increases encapsulation. • Nested classes “can” lead to more readable and maintainable code. • Child to parent class connection is simpler as it visually illustrates the variables and methods of each class.
- 11. Page 10Classification: Restricted Topics to be covered in next session • Java IO • Files • Streams • Byte-based • Character-based • Object Serialization