CS 241 – Computer Programming II Lab Kalpa Gunaratna –

Contact  Contact by   Office hours  376 Joshi  Mondays & Wednesday 3:00 pm – 4:00 pm

Inheritance  Example : A B B is a sub class of A A is the parent class B is the child class

 Use extends keyword. public class A { int x = 5; A() { } A(int x) { this.x = x; } public int getX() { return x; } public class B extends A { int y = 10; B(int y) { this.y = y; }

 If you do not have the default constructor, you have to call specifically a constructor by keyword super in the child class. public class A { int x = 5; A(int x) { this.x = x; } public int getX() { return x; } public class B extends A { int y = 10; B(int y) { super(5); this.y = y; }

 If you want to get parent class’s method behavior to a child class’s method, the parent method should be called in the first place in your child method using the keyword super and equivalent parameters. public class A { int x = 5; A(int x) { this.x = x; } public int getX() { return x; } public int calAge(int val) { int z = val * x; return z; } public class B extends A{ int y = 10; B(int y) { super(5); this.y = y; } public int calAge(int val) { int k = super.calAge(val); k += 3; return k; }

In lab  You need to understand extends & super keywords.  Do not use protected or instanceOf keywords.  Modify the two classes so that no code is redundant and Trekkie is a sub class of Geek.  Change code where necessary but the output should match to the original code output.

Post lab  Make classes as explained in the assignment.  Use polymorphic objects (geeks) in your test code.  Draw an UML class diagram for all of your classes so that it clearly represents inheritance from one to another.  Submit the UML diagram with your project to WebCT.