Texas Computer Science 2

In this lesson students learn about classes and objects, the foundation of Object Oriented Programming. This lesson introduces a lot of new vocabulary, but it will be reinforced and used in concrete examples and exercises over the next several lessons.

Students have been creating objects of the String class, they just haven’t dove into that terminology yet. In this lesson, students will learn about objects, which are things that have state and behavior, and classes, which are the templates for creating objects. Students will be creating instances of objects in this lesson.

In this lesson, students will dive deeper into the relationship between classes, objects, and instances (generally instances and objects refer to the same thing). Students will get more practice identifying classes and objects, creating objects from classes, and calling methods on objects.

In this lesson, students learn about the overarching idea of “using a class as a client”. In Java, everything is represented as a class. Classes are a nice way of bundling up functionality. There are classes written for a lot of common needs (such as the String class and the Character class), and we can use these classes in our programs.

When someone else creates a class, and you use the functionality of that class, that is called being a client of the class. Users don’t need to know exactly how everything works inside the class, they can just use all the functionality of that class without worrying about the inner workings. For example, you can use the String class to create String objects, and call methods on the objects to get information like the length and the characters at certain indices, without ever looking at the source code for the String class.

Now that students have had practice using classes without actually changing the source code for a class, they dive in and actually start writing our own classes. In this lesson, students will learn the basics of writing classes including implementing constructors, using instance variables, and writing a toString method.

In this lesson, students will learn about instance methods and start adding more interesting instance methods to their classes. The instance variables define the state of an object (instance), and the instance methods define the behavior of an object (instance). Instance methods give the object new abilities, they define what the object can actually do.

toString is one example of an instance method, it returns the instance’s (object’s) instance variables put together as a String, that way the instance can be printed out to the screen. It gives an object the ability, or the behavior, to represent itself as a String. In this lesson, we’ll start adding more instance methods to our classes.

In this lesson students will learn about a special type of instance method: getter and setter methods. Getter and setter methods give the client access to the private instance variables in a class. Programmers don’t want to make instance variables public because then the client has full access to them, and might accidentally do something that messes them up (for example, it doesn’t make sense to have a negative width or a negative height for a Rectangle object). Instead, programmers expose limited access to them through getter and setter methods. That way, they can allow only certain changes to the instance variables, and block other changes.

In this lesson students learn about Class methods and Class variables, which are different from Instance methods and Instance variables.

Students have learned a lot about Instance methods and Instance variables. Each instance of a class has its own instance methods, and its own instance variables. For example, two different Rectangle objects can each have their own width and their own height. These values can be different from instance to instance.

The key difference with Class methods and Class variables is that all instances share the exact same Class methods and Class variables. Each instance does not get its own copy, it is all shared among instances. These methods and variables exist at the Class level, not the Instance level.

Class methods and Class variables are specified using the static keyword.

In this lesson, students will learn how to convert primitive types to object types using a wrapper class. They will learn how Java automatically converts types using autoboxing and unboxing.

In this lesson students will learn about method overloading: writing several different methods, each with the same name. As long as each method’s parameter list is different, method can use the same name multiple times!

In this lesson students explore the scoping of a variable, which is where the variable is “defined” or where it exists. In this lesson getting students to define and explain the concept themselves is key.

In this lesson students learn several new vocabulary terms about Classes and Object Oriented Programming. There’s a lot of vocab in this lesson, but it’s all important for the AP exam. Many of these terms students have seen before, however this lesson will describe what they mean.

The most important term to learn is the this keyword. this is a reference to the current instance. this is used to avoid naming conflicts between instance variables and parameters.

In this lesson, students learn about the difference between primitive and object variable types. So far, students have used these different variable types, but have not explored the differences between the two.

This lesson looks at the differences between primitive and object types and discusses the implications of these differences.

In this lesson, students learn about class hierarchy and make subclasses and superclasses. Class hierarchy is a critical part of the Java language and used to help reuse code between classes.

Students will explore the relationships of classes in this lesson and then extend that to class design in the next lesson.

In this lesson, students learn about class structure and how we can further enhance that class structure with abstract classes. They will then use this knowledge to implement abstract classes.

Abstract classes are a key concept for polymorphism. In this lesson, students will get the knowledge of how to use abstract classes, but some of the reasons why we implement them will become more apparent in the next lesson.

In this lesson, students learn about polymorphism and how it applies to dynamic binding at run time. Students will also explore how polymorphism can be used as a formal parameter in methods or as a declaration type for arrays or ArrayLists.

In this lesson, students will call and use the Object superclass. The Object class is the superclass of all other classes in Java.

In this lesson, students will learn about interfaces. Interfaces share a lot of similarities with abstract classes and part of this lesson will focus on comparing the two.

Students will make and implement their own interfaces as well as implementing interfaces that are created by Java.

In this lesson, students learn about composition and utilize composition to reuse code.

In this lesson, students will explore several areas related to the ethical and societal implications of computing systems. This includes the professional computing code of ethics, system reliability, legal issues and intellectual property concerns, and bias in computing. This lesson corresponds with AP Computer Science A topic 5.10.

In this lesson, students demonstrate content knowledge of the unit’s learning objectives.