Chapter 6 Methods 227 (Php web hosting) A local variable
Chapter 6 Methods 227 A local variable or reference declared in a block can be used only in that block or in blocks nested within that block. Members of a class have class scope and are visible in what is known as the declaration space of the class. Class scope enables a class s methods to access directly all members defined in that class or inherited into that class. (static members are an exception to this rule.) Any variable declared in the initialization portion of a for structure will be visible only within that for structure. A recursive method is one that calls itself either directly, or indirectly through another method. A recursive method knows how to solve only the simplest case(s), or base case(s). If the method is called with a base case, the method returns a result. If the method is called with a more complex problem, the method divides the problem into two conceptual pieces a piece that the method knows how to solve (base case) and a piece that the method does not know how to solve. To make recursion feasible, the portion of the problem that the method does not know how to solve must resemble the original problem, but be a slightly simpler or smaller version. Certain recursive methods can lead to an exponential explosion of method calls. Both iteration and recursion are based on a control structure. Iteration uses a repetition structure (such as for, whileor do/while); recursion uses a selection structure (such as if, if/else or switch). Both iteration and recursion involve repetition. Iteration explicitly uses a repetition structure; recursion achieves repetition through repeated method calls. Iteration and recursion each involve a termination test. Iteration terminates when the loop-continuation condition fails; recursion terminates when a base case is recognized. Both iteration and recursion can execute infinitely. An infinite loop occurs with iteration if the loop-continuation test never becomes false; infinite recursion occurs if the recursion step does not reduce the problem in a manner that converges on the base case. A recursive approach normally is chosen in preference to an iterative approach when the recursive approach more naturally mirrors the problem and results in a program that is easier to understand and debug. Several methods can have the same name, as long as these methods have different sets of parameters, in terms of number of parameters, types of the parameters and order of the parameters. This is called method overloading. Method overloading commonly is used to create several methods with the same name that perform similar tasks, but on different data types. TERMINOLOGY .(dot operator) coercion of arguments argument to a method call comma-separated list of arguments automatic duration complexity theory automatic initialization of a variable constant variable base case control structures in iteration Buttonclass control structures in recursion calling method divide-and-conquer approach cast operator duration of an identifier class event handling Click event exhausting memory
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