Introduction to Objects

Objects have a name, member variables, and methods. They can be represented by a CRC card (Class-Responsibility-Collaboration) when designing programs. Here is an example of a CRC card:

More information on CRC cards can be found here.

1. Create a Duck class in your java project. Add its member variables and methods to match the CRC card. Now add the code for the constructor of the Duck class:

Duck(String favoriteFood, int numberOfFriends) {
       this.favoriteFood = favoriteFood;
       this.numberOfFriends = numberOfFriends;
}

2. Now pick your favorite animal and describe it in CRC form with at least 2 member variables and 2 methods (write it on the whiteboard).

3. Create a java class for your animal including:

      member variables
      methods(with sysouts)
      a constructor that sets the member variables


4. Create a new java class. This will be a "runner" or "driver" class, so it will need a main method.

5. In your runner class, create a Duck object (instance) by calling its constructor as follows:

Duck daffy = new Duck("donuts",5);

      Now you have a duck object, you can make it quack:

daffy.quack();

6. Now create an instance of your animal (Hint: see step 5 above) and call its methods.