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Adding and Eating Worms

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

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Adding and Eating Worms

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

  2. 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

  3. 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.

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

  5. 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?

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

  7. 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???

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

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

  10. 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

  11. The code if (this.canSee(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.

  12. 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.

  13. 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.

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

  15. 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 */

  16. 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. */

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

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

  19. 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.

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

  21. 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();

  22. 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();

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