Abstraction
|
Abstraction is a
process of hiding the implementation details and showing only functionality
to the user. Another way, it shows only important things to the user and
hides the internal details.
|
Achieve Abstaction
|
There are two ways
to achieve abstraction in java
1. Abstract class (0
to 100%)
2. Interface (100%)
|
Abstract
class
|
A class that is
declared as abstract is known as abstract class.It needs to be extended and
its method implemented. It cannot be instantiated.
Example :
abstract class A
{
// abstract methods
// some concrente methods
}
|
abstract
method
|
A method that is
declared as abstract and does not have implementation is known as abstract
method.
|
abstract
return_type <method_name>();//no braces{}
Example :
abstract void
test();
abstract int
method (inti) ….. etc
It should be
used abstract keyword
Small points on abstract class :
Example:
abstract class F
{
Variables
declaration possible
static int i;
int j;
A I;
Methods
declaration can’t possible
//void test();
//static void test();
Methods
implements possible
static void test1()
{
}
int test2()
{
//Some stmts
Return 10;
}
Blocks
SIB
static
{
System.out.println("hi static");
}
IIB
{
System.out.println("hi");
}
Final
Keyword can’t be used in abstract class
/*abstract final A
{
}*/
Void test9()
{
System.out.println(“over
riding before”);
}
abstract void tet2();
Abstrac method implementation not possible
//abstract void test5()
{
}
Object
Cration not possible by using new keyword
//F f1=new F();
Constructer
is possible in abstruct class
F()
{
System.out.println("F()");
}
Inner
Classes are possible in side abstract class
class D
{
}
private class R
{
}
}
abstract class T extends F
{
void test2()
{
}
Overriding possible in abstract
class
Void test9()
{
System.out.println(“over
riding before”);
}
}
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