java abstract class,concrete class and interface

Dummies In Java · **Posted:** Thu Jan 22, 2009 5:22 pm

what is the meaning of abstract class,concrete class and interface ?
can give example of each.

thanks

msi_333 · **Posted:** Thu Jan 22, 2009 8:09 pm

1. In Java there is no multipliable inheritance like in C++ .But you can implement more thank one interface .
The interface methods are all abstract , this means contain no body ,and all properties are public static final (Means can't be changed later) . In interface you just say what is the class but don't say how to do it . Methods of interface are public and abstract by defaults and you don't need write the modifiers. interface can extend one or more interfaces .

Example

Code:

 interface shape 
{
         public abstract void   draw(); 


 } 

Here a class circle implements the shape interface.

Code:

class shape implements shape
{
          public void draw()
                        {
                          // Draw body 
                         }


}  

2. Abstract class can have implemented methods and others not , you can't have an abstract method in non abstract class. you have alway to remember to that abstract methods end with semicolon . example

Code:

public abstract class Vehicle {
private String type;
public abstract void goUpHill(); // Abstract method
public String getType() { // Non-abstract method
return type;
}
}
public abstract class Car extends Vehicle {
public abstract void goUpHill(); // Still abstract
public void doCarThings() {
// special car code goes here
}
}
public class Mini extends Car {
public void goUpHill() {
// Mini-specific going uphill code
}
}

i hope i helped you .

Bluerose · **Posted:** Sat Mar 21, 2009 4:53 am

Thank you for this information. I was facing an exam and the difference of these abstracts and interfaces confuses me a bit and now i am cleared. Thank you for the question raised by Dummies in Java and the explanation as well from msi_333

msi_333 · **Posted:** Sat Mar 21, 2009 5:10 pm

you are welcome .

java abstract class,concrete class and interface

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