Enforcing rules with accessor methods in Java

Generator Code 3/9 in Java Enforcing rules with accessor methods

Go back to Listing 7-8 and take a quick look at the setName method Imagine putting the method s assignment statement inside an if statement public void setName(String n) { if (!nequals( )) { name = n; } } Now, if the programmer in charge of the UseAccount class writes myAccount setName( ), the call to setName doesn t have any effect Furthermore,

because the name variable is private, the following statement is illegal in the UseAccount class: myAccountname = ; Of course, a call such as myAccountsetName( Joe Schmoe ) still works because Joe Schmoe doesn t equal the empty string That s cool With a private variable and an accessor method, you can prevent someone from assigning the empty string to an account s name variable With more elaborate if statements, you can enforce any rules you want

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nce upon a time, there was a beautiful princess When the princess turned 25 (the optimal age for strength, good looks, and fine moral character), her kind father brought her a gift in a lovely golden box Anxious to know what was in the box, the princess ripped off the golden wrapping paper When the box was finally opened, the princess was thrilled To her surprise, her father had given her what she had always wanted a computer program that always ran correctly The program did everything the princess wanted and did it all exactly the way she wanted it to be done The princess was happy, and so was her kind, old father As time went on, the computer program never failed For years on end, the princess changed her needs, expected more out of life, made increasing demands, expanded her career, reached for more and more fulfillment, juggled the desires of her husband and her kids, stretched the budget, and sought peace within her soul Through all this, the program remained her steady, faithful companion As the princess grew old, the program became old along with her One evening, as she sat by the fireside, she posed a daunting question to the program How do you do it she asked How do you manage to keep giving the right answers, time after time, year after year

Clean living, replied the program I swim twenty apps each day, I take C++ to Word off viruses, I avoid hogarithmic algorithms, I link Java in moderation, I say GNU to bugs, I don t smoke to backup, and I never byte off more than I can queue Needless to say, the princess was stunned

Defining a Class (What It Means to Be an Employee)

Wouldn t it be nice if every piece of software did just what you wanted it to do In an ideal world, you could just buy a program, make it work right away, plug it seamlessly into new situations, and update it easily whenever your needs change Unfortunately, software of this kind doesn t exist (Nothing of this kind exists) The truth is, no matter what you want to do, you can find software that does some of it, but not all of it This is one of the reasons why object-oriented programming has been so successful For years, companies were buying prewritten code only to discover that the code didn t do what they wanted it to do So what did the companies do about it They started messing with the code Their programmers dug deep into the program files, changed variable names, moved subprograms around, reworked formulas, and generally made the code worse The reality was that if a program didn t already do what you wanted it to do (even if it did something ever so close to what you wanted), you could never improve the situation by mucking around inside the code The best option was always to chuck the whole program (expensive as that was) and start all over again What a sad state of affairs! With object-oriented programming, a big change has come about At its heart, an object-oriented program is made to be modified With correctly written software, you can take advantage of features that are already built-in, add new features of your own, and override features that don t suit your needs And the best part is that the changes you make are clean No clawing and digging into other people s brittle program code Instead, you make nice, orderly additions and modifications without touching the existing code s internal logic It s the ideal solution