Everything in Java is associated with classes and objects, along with its attributes and methods. If you write code in a parent class, you usually don’t need to write it again in associated child classes; doing so would be inefficient and would make a program more difficult to read. First, Stack is inherited from Vector, which says that a Stack is a Vector, which isn’t really true from a logical standpoint. The only thing that can occur to the class interface during the upcast is that it can lose methods, not gain them. This means that inside the method you cannot change what the argument reference points to: The methods f( ) and g( ) show what happens when primitive arguments are final: you can read the argument, but you can't change it. Also note the way that Orc’s toString( ) method is defined in terms of the base-class version of toString( ). It makes sense that the compiler doesn’t just create a default object for every reference, because that would incur unnecessary overhead in many cases. In this chapter you’ll see two ways to accomplish this. When the user knows you’re assembling a bunch of parts, it makes the interface easier to understand. Code reuse is alleged to be one of the prime benefits of object-oriented programming. A Java JDBC PreparedStatement is a special kind of Java JDBC Statement object with some useful additional features. GC for instance. Feedback, Primitives that are fields in a class are automatically initialized to zero, as noted in Chapter 2. ", 0).charAt (0); c2 = keyboard.findWithinHorizon (". Java's multithreading system is built upon the Thread class, its methods, and its companion interface, Runnable. available in the derived class. But to be revolutionary, you’ve got to be able to do a lot more than copy code and change it. If your class doesn’t have default arguments, or if you want to call a base-class constructor that has an argument, you must explicitly write the calls to the base-class constructor using the super keyword and the appropriate argument list: If you don’t call the base-class constructor in BoardGame( ), the compiler will complain that it can’t find a constructor of the form Game( ). Feedback, The following sections discuss the three places where final can be used: for data, methods, and classes. BoxAdcontent.document.close(); If it is, it can reclaim objects in any order it wants. BoxAdcontent.document.write("