If you've been reading this book sequentially, you've read all about the core Java language constructs, including the object-oriented aspects of the language and the use of threads. Now it's time to shift gears and start talking about the Java Application Programming Interface (API), the collection of classes that comprise the standard Java packages and come with every Java implementation. Java's core packages are one of its most distinguishing features. Many other object-oriented languages have similar features, but none has as extensive a set of standardized APIs and tools as Java does. This is both a reflection of and a reason for Java's success. Table 10-1 lists the most important packages in the API and shows which chapters discuss each of the packages.
As you can see in Table 10-1, we have examined some classes in java.lang in earlier chapters while looking at the core language constructs. Starting with this chapter, we throw open the Java toolbox and begin examining the rest of the API classes, starting with text-related utilities, because they are fundamental to all kinds of applications.