Java™ Application Development on Linux - Dator

3.8 Review95straight Java facts so we can let the non-C++ folks move on while we go a littledeeper with you C++’ers.In Java, a method or a class may be declared final. A method that is declaredfinal may not be overridden in classes that extend the class containingthe final implementation. A class that is declared final may not be extendedat all.Now, the comparisons to C++ require us to talk about a language featurethat does not exist at all in Java. In C++, unless a method is declared virtual,when a class is used by reference to a base class (for example, when usingEmployee as a Person), the base class version of the method is called. If themethod is declared virtual, the version of the method called is the version forthe type of Person referenced (in this case, Employee). In Java, all methodsare virtual. There is no such keyword in Java.3.7A USEFUL SIMPLE APPLICATIONWe will use the sample application shown in Example 3.30 in other sectionsof this book to illustrate the use of Java tools. This example is so simple (a singleclass) that it doesn’t demonstrate the object-oriented aspect of development,but it does make use of some APIs that take advantage of it. We will not walkyou through this application right here, but present it as a listing of a completeJava class. Not all of the APIs used in this example will be explained, so youmay want to refer to the Javadoc pages for explanations of object types ormethod calls that don’t seem obvious.3.8REVIEWWe’ve taken a very quick look at the syntax of Java statements, classes, andinterfaces. Much of the syntax is very reminiscent of C, though Java’s objectorientedfeatures differ in significant ways from C++. We looked at how to putJava classes into packages, and at the implications of this for locating the.class files.We also showed what the HTML-based Javadoc documentation lookslike. These HTML pages will likely be a handy reference for you as you designand write your Java code.