What does the keyword extends mean in BlueJ?

Answer 1

The "extends" keyword in Java is how you declare a subclass.

class Base {

void foo() {}

}

class Sub extends Base { //Sub is now a subclass of Base

void begin()

{

Sub s = new Base(); //cannot do this the other way around!

}

}

Answer 2

The extends keyword is used for inheritance. The extends keyword is used in the derived class to indicate that a particular class (the derived class) is inheriting the characteristics of the base class.

e.g.

public class base_class

{

public void method_name()

{

body;

}

}

public class Extended_Class extends base_class

{

public void method_name()

{

body;

}

}