The Collections Framework
The java.util package contains some of the most. exciting enhancements added by Java 2: collections. A collection is a group of objects. The addition of collections . caused fundamental alterations in the structure and architecture of many· elements in java.util. It also expanded the domain of tasks to which the package. can be' applied. Collections are a state-of-the-art technology that merits close attention byall . Java programmers. In addition to collections, java.util contains a wide assortment of classes and interfaces that 'support a broad range of functionality. These classes and interfaces are used throughout the core Java packages and, of course, are' also available for use in programs that you write. Their applications Include generating pseudorandom·' numbers, manipulating date and time, observing events, manipulating sets of bits, and tokenizing strings. Because of its many features, java.util is one of Java's most widely used packages.
The. java.util classes are listed here. The ones added by Java 2 are so labeled
The ResourceBundle, Listltesourcellundle, and PropertyResourceBundle classes aid in the internationalization of large programs with many locale-specific resources. These classes are 'not examined here. Property Permission, which allows you to grant a read/write permission to a system property, is also beyond the scope of this book. EventObject and EventListener are described in Chapter 20. The remaining classes and interfaces are examined in detail. ' Because java.util is quite large, its description is broken into two chapters. This . chapter examines those members of java.util that relate to collections of objects.