Java interface
Q.1 what is the interface?
v Interface is similar to an abstract class but having all
the methods of abstract type interface are the blueprint of the class it
specifies what a class must do and mot now.
v Interface is a mechanism to achieve abstraction in
java.
v Since the java
8th version we add default and
static methods in an interface.
v Since the java
9th version we add default and
private methods in an interface.
Write a program interface?
interface Test
{
public abstract void show ();
}
class Test1
implements Test {
public void show () {
System.out.println(“one”)
}
public static void
main(String args[]) {
Test1 t1= new
Test1();
t1.show();
}
}
An interface can support multiple inheritances?
Ø Yes we can achieve multiple inheritances by using an interface.
Example:-
interface Test
{
public abstract void show ();
}
interface Test1
{
public abstract void show1 ();
}
class Test3
implements Test1, Test2 {
public void show () {
System.out.println(“one”)
}
public void show1 () {
System.out.println(“two”)
}
public static void
main(String args[]) {
Test2 t1= new
Test2();
t2.show();
t2.show1();
}
}
interface class example
interface A1 {
abstract void show ();
}
v It is used to
achieve abstraction.
v It supports multiple inheritances.
v It can be used to achieve loose coupling.
Why use the java interface?
v It is used to achieve abstraction
v By interface we can
support the functionality of multiple inheritances
v It can be used to achieve loose coupling.
v Similertices between abstracts class and interfaces:-
v Both can contain abstract method
v We cannot create an instance of abstracts class and interfaces.
What is loose coupling?
v Loose coupling is a design goal that seeks to reduce the
interdependencies between components of the system to reduce the risk that changes in one component will require changes
in any other component. Loose coupling is a much more generic concept intended to increase the flexibility of the system make it more
maintainable and makes the entire framework more stable.
Syntax:--
interface Test
{
abstract void show ();
}
Ø Fields –public/static /final/ access modifier
Ø After 8th
version add feature
Ø Default concreate method
Ø Static method
Ø After 9th version add
Ø Privet method
Example:-
interface Test
{
abstract void show() ; }
public final int a=10;
default void display() {
System.out.println(“one”)
}
static void run() {
System.out.println(“programming
khata”)
}
privet void show() {
System.out.println(“programming
khata”)
}
}
Example1:-
interface Test
{
public abstract void show()
; } //main function of the interface
Example2:-
interface Test
{
public abstract void show()
;
default void show()
{
System.out.println(“one”)
}
}
Example3:-
interface Test
{
public abstract void show()
;
default void show()
static void show()
{
System.out.println(“one”)
}
}
Example4:-
interface Test
{
public static final int a=10;
public abstract void show()
;
default void show()
{
// statement hare
}
static void show()
{
System.out.println(“one”)
}
}
Write a program interface?
interface Test
{
public abstract void show ();
}
class Test1
implements Test {
public void show () {
System.out.println(“one”)
}
public static void
main(String args[]) {
Test1 t1= new
Test1();
t1.show();
}
}.
Example:-
interface Test
{
public abstract void show ();
}
interface Test1
{
public abstract void show1 ();
}
class Test3
implements Test1, Test2 {
public void show () {
System.out.println(“one”)
}
public void show1 () {
System.out.println(“two”)
}
public static void
main(String args[]) {
Test2 t1= new
Test2();
t2.show();
t2.show1();
}
}
|
Abstract class |
Interface class |
|
1. Class
can have instances method that implements a default behavior.
|
2. Method
of a java interface are implements abstracts and
cannot have implementation. |
|
3. An
abstract class may contain a not-final
variable. |
4. Interface
contains public, static, final, variables only |
|
5. Method
& variable can have any. access modifier i.e public, static default, and
private. |
6. Method
variables are always public |
|
7.
Java
abstract class should be extended using the “extends” keyword |
8.
Java
interface should be implimentaited
using. Implementation keyword |
|
9. An abstract class can extend another Java class and
Implement multiple java interface |
10. In
interface can extend another Java
interface only. |
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