ITSC 1213 - Introduction to CS 2 How to Design Programs with Object Oriented Programming

Subsection 6.6.1 What are Objects and Classes?

• Java is an object-oriented programming language that can be used to model objects in the real world. We’ve seen that Java programs start with public class. A class is used to define a new data type or a blueprint for objects.

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• Objects are the variables created from a class definition, and they are instances of a class.

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• You can think of a class like a blueprint or a cookie cutter. It is used to create the cookies (objects) and can be used to create as many cookies (objects) as you want.

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• You can think of a class as the type or classification. Each type can have attributes (the object’s properties or what it knows about itself) and behaviors (what an object does). In Java code, the attributes are written as instance variables in the class, and the behaviors are written as methods.

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• when we declare a variable like String name;, we are creating a String object using the built-in String class, which provides predefined methods for handling text.

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• We can define and use our own classes, such as Person, Monster, Student, where we specify attributes and behaviors tailored to our specific needs.

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• The dot operator (.) is used to run an object’s method. You can think of the (.) as asking the object to do something (execute one of its methods). For example, .toUppoerCase() asks the String object to create a new string by converting all of the characters in this String to upper case.

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• The parentheses () after a method name are there in case you need to give the method arguments (some data) to do its job, for example the equals(...)

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Subsection 6.6.2 Practice