Java™ Application Development on Linux - Dator

3.4 Encapsulation, Inheritance, and Polymorphism89private String hidn;String pkgstr;protected String protstr;public String wideOpen;3.4.2.2 The static statementAnother keyword qualifier on declarations that we need to describe is thestatic keyword. When a variable is declared static then there is only oneinstance of that variable shared among all instances of the class. Since the variableexists apart from a particular instance of the class, one refers to it with theclass name followed by a dot followed by the variable name, as in System.out.Similarly, methods can be declared static as well. This also means thatyou don’t need an instance of the class to call them, just the class name, as inSystem.getProperties().Now with Java 5.0, you don’t even need the class name, provided that youhave a static import statement at the top of your class, for example:import static java.lang.System.*;3.4.2.3 The final statementAnother way that static is often seen is in conjunction with the final keyword.When a variable is declared final then a value can be assigned to it once,but never changed. This can make for good constants.Since public will make the variable visible to all other classes, staticwill make it a class variable (available without an instance of that class), andfinal will keep it from being altered (even though it is publicly available), thencombining all of those gives us a good declaration for a constant, for example:public static void long lightSpeed = 186000;// mpsNew to Java 5.0 is the explicit creation of enumerated types. Prior to 5.0,programmers would often use static final constants even when the particularvalue was unimportant, as a way to provide compile-time checking of theuse of the constant values. Here is an example of a declaration of a set ofenumerated values:enum WallMods { DOOR, WINDOW, VENT, GLASSBLOCK };