Adding and Eating Worms Mrs. C. Furman August 23, 2010

Let’s add a Worm Class  What class should we extend to add a Worm?  Worm is-a Animal  Select New Subclass from the Animal menu Click here

Setting up the new Subclass  Enter the name as Worm  Class names in Java should always start with a capital letter  Rules for class names:  Start with a capital letter  Contain only letters, numbers or underscores  Can’t be a keyword  As a convention it should describe the class.

Name and add a picture  After you name the class  Add a picture. Choose the worm.png  Select ok

Exercise  Compile  Add some worms and crabs to the world.  Run the scenario  What happens to the worms?  What happens when a crab meets a worm?

How can we get Crabs to Eat Worms?  What would we need to be able to do to get Crabs to eat Worms?

Making Crab Eat Worms  Lets see if there are any classes in Animal that can help us…  Open the source code, and choose documentation.  Any methods???

boolean canSee(java.lang.Class clss)  What is the return type?  What is the method name?  What is the parameter?

void eat (java.lang.Class clss)  What is the return type?  What is the method name?  What is the parameter?

Using canSee and eat to eat worms.  canSee - will tell us is there is a worm near us.  it returns true or false  eat – eats the worm

The code if (this.canSee(Worm.class)) { this.eat(Worm.class); this.eat(Worm.class);}  Worm.class – this specifies the class we are looking for and eating.  Add the above if statement to the act method.

Adding Methods  Our methods should specify a single “behavior” that we want to perform.  act is starting to have too many behaviors that it is charged with.

lookForWorm method  We would like to create a lookForWorm method that contains the if statement we just added to act.  It will look for worms and then eat them.

Comments  When we add a new Method, we will want to add a description of what the method does.  What does lookForWorms do?

Different Types of Comments  // - used to generate a single line of code  /* - starts a multiple line of comment and ends with */  /** - starts a javadoc comment. This will generate the documentation we see when we open the code. It also ends with */

Comment /** * Check whether we have found a worm * If we have found a worm, we eat it. * If we haven’t, we do nothing. * PostCondition: After this method has * been executed worms near the crab * have been removed. */

Adding the method  Is our method an action or a question?  What should our return type be?

Add the method public void lookForWorm() { if (this.canSee(Worm.class) ) if (this.canSee(Worm.class) ) { this.eat(Worm.class); this.eat(Worm.class); }}

Modify Act method  Remove the eating if statement from act  Replace with a call to the lookForWorm method  this.lookForWorm();  Compile and Run the code.

Other Methods  Are there other behaviors in Act that can be pulled out into a method?

Exercise  Create method randomTurn.  What would the return type be? Is it a question, or an action?  Move the code that does the random turning out of Act and put it into randomTurn.  Replace the code in Act with a call to this.randomTurn();

Exercise  Create another method for turning at the edge called turnAtEdge  What is the return type? Is it a question, or an action?  Remove the code from Act and move it into turnAtEdge. Replace the code in Act with a call to this.turnAtEdge();