Abstraction is defined as the hiding of backend content/details and only providing necessary information.
There are two ways to achieve abstraction:-

• Abstract class
• Interface

abstract class area{
abstract void rectangle(double x, double y);
}
class findarea extends area{
void rectangle(double x, double y)
{
double ar=x*y;
system.out.println("Area of rectangle-" +area);
}
class ar{
public static void main(string args[])
{
double x,y;
area ar= new area();
system.out.print("enter length and breadth of rectangle-");
x=get.nextDouble();
y=get.nextDouble();
area.rectangle(x,y);

output- "enter length and breadth of rectangle-"

INTERFACE:-An interface is a way for achieving fully abstraction and multiple inheritance.
e.g of interface is:

interface  Area
{
double compute(double x,double y);

}
class Rect implements Area
{
public double compute(double x,double y)
{
return x*y;
}
}


class findarea
{
public static void main(String arg[])
{
Area A;
Rect r=new Rect();
A=r;
System.out.println(The Area of rectangle is:+A.compute(30,20));
}
}

output- " The area of rectangle is-600"