Java™ Application Development on Linux - Dator

70Chapter 3An Experienced Programmer’s Introduction to JavaAs in the if and while statements, the braces are optional when only asingle statement is involved, but good practice compels us always to use thebraces. Additional code can easily be added without messing up the logic—should one forget, at that point, the need to add braces.Speaking of the while loop: When do you use a for and when do youuse a while loop? The big advantage of the for loop is its readability. It consolidatesthe loop control logic into a single place—within the parentheses.Anyone reading your code can see at once what variable(s) are being used tocontrol how many times the loop executes and what needs to be done on eachiteration (e.g., just increment i). If no initialization is needed before startingthe loop, or if the increment happens indirectly as part of what goes on in thebody of the loop, then you might as well use a while loop. But when the initializationand iteration parts can be clearly spelled out, use the for loop forthe sake of the next programmer who might be reading your code.The for loop with iterators. As of Java 5.0, there is additional syntax for afor loop. It is meant to provide a useful shorthand when looping over themembers of an iterator. 4 So what’s an iterator? Well, it has to do with collections.Uh, oh, we’re surrounded by undefined terms. One step at a time, here.Java has a whole bunch (we won’t say “collection,” it’s a loaded term) of utilityclasses that come with it. We mentioned these classes in our discussion ofJavadoc. While not part of the language syntax, some of these classes are souseful that you will see them throughout many, if not most, Java programs.Collection is a generic term (in fact, it’s a Java interface) for several classesthat allow you to group similar objects together. It covers such classes as Lists,LinkedLists, Hashtables, Sets, and the like. They are implementations ofall those things that you (should have) learned in a Data Structures course inschool. Typically you want to add (and sometimes remove) members from acollection, and you may also want to look something up in the collection. (Ifyou’re new to collections, think “array,” as they are a simple and familiar typeof collection.) Sometimes, though, you don’t want just one item from the collection,but you want to look at all of the objects in the collection, one at atime. The generic way to do that, the way that hides the specifics of what kindof collection you have (linked list, or array, or map) is called an iterator. 54. This feature is related to the topic of templates and generics. See Section 3.5.5. The earliest versions of Java used an object called an Enumeration. It does much the samething as an iterator, but with somewhat clumsier method names. Iterators also allow for a