Java in a Nutshell, 6th Edition

Chapter 5. Introduction to Object-Oriented Design in Java

In this chapter, we’ll look at how to work with Java’s objects, covering the key methods of Object, aspects of object-oriented design, and implementing exception handling schemes. Throughout the chapter, we will be introducing some design patterns—essentially best practices for solving some very common situations that arise in software design. Towards the end of the chapter, we’ll also consider the design of safe programs—those that are designed so as not to become inconsistent over time. We’ll get started by considering the subject of Java’s calling and passing conventions and the nature of Java values.

Java Values

Java’s values, and their relationship to the type system, are quite straightforward. Java has two types of values—primitives and object references.

Note

Some books refer to primitives as “value types”—this makes it confusing to think of object references as a value in Java. For this reason, we stick to the term primitive when discussing any of Java’s eight nonreference types.

These two kinds of values are the only things that can be put into variables. In fact, that’s one way to define a value: “a thing that can be put into a variable or passed to a method.” For C++ and C programmers, note that object contents cannot be put into variables—so there is no equivalent of a dereference operator or a struct.

The key difference between primitive values and references is that primitive values cannot be altered—the value ...