University of Washington, CSE 142

Lab 8: Classes and Objects

lab document created by Marty Stepp, Stuart Reges and Whitaker Brand

Basic lab instructions

Mouse over highlighted words if you're not sure what they mean!
Talk to your classmates for help.
You may want to bring your textbook to future labs to look up syntax and examples.
Stuck? Confused? Have a question? Ask a TA for help, or look at the book or past lecture slides.
Complete as much of the lab as you can within the allotted time. You don't need to keep working on these exercises after you leave.
Feel free to complete problems in any order.
Make sure you've signed in on the sign-in sheet before you leave!

Today's lab

Goals for today:

write our own new classes of objects
declare fields, methods, and constructors
understand the difference between class code and client code
Practice working with the critter classes and defining your own critter class.
Through a series of exercises, you will make a LabTA critter more and more complex in terms of its behaviors. The LabTA class will serve as a model for how to solve the homework.
Where you see this icon, you can click it to check the problem in Practice-It!

Declaring a class (syntax)

public class ClassName {
    // fields
    fieldType fieldName;

    // methods
    public returnType methodName() {
        statements;
    }
}

A couple things look different than programs for past homeworks:

no main method. It won't be run like a client program.
methods don't have the static keyword in the header.
variables declared outside of any method (fields) are visible in every method.

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If you finish them all...

If you finish all the exercises, try out our Practice-It web tool. It lets you solve Java problems from our Building Java Programs textbook.

You can view an exercise, type a solution, and submit it to see if you have solved it correctly.

Choose some problems from the book and try to solve them!