Anatomy of an enhanced for loop in Java

Generate Code-39 in Java Anatomy of an enhanced for loop

Listing 6-2:

for (int count = 1; count <= 10; count++)

Listing 6-5:

for (Suspect mySuspect : Suspectvalues())

In both kinds of loops, you define a variable The loop in Listing 6-2 defines a variable named count The loop in Listing 6-5 defines a variable named mySuspect In both listings, the statements inside the loop refer to the newly defined variable The loop in Listing 6-2 has the statement outprint(count); and the loop in Listing 6-5 has the statement outprint(mySuspect); During successive iterations, the print in Listing 6-2 stands for outprint(1), outprint(2), and so on During successive iterations, the print in Listing 6-5 stands for outprint(mustard), outprint(plum), and so on In both kinds of loops, you declare the type of value that the variable can have In Listing 6-2, the variable count must store an int value ( 7, 0, 5, 15, and so on) In Listing 6-5, the variable mySuspect must refer to a Suspect value (mustard, plum, white, and so on) In fact, this declaring the type of value rule applies everywhere in Java not only in for loops Every Java variable belongs to one type or another In Listing 6-1, the line int numGuesses = 0; declares that numGuesses must store an int value The line goes on to say that, among all possible int values, the starting value for numGuesses is 0 Again in Listing 6-1, the line Scanner myScanner = new Scanner(Systemin); declares that myScanner must refer to a Scanner object Among all such objects, the starting value for myScanner is an object that gets keystrokes from the keyboard (from Systemin) In both kinds of loops, you specify a range of values You specify the range of values that the variable takes on during the execution of the loop In Listing 6-2, you narrow the count variable s values to the numbers from 1 to 10 In Listing 6-5, you throw caution to the wind, and say that mySuspect gets to be every one of the items in Suspectvalues()

You can apply values() to the name of any enum type In fact, to create a n enhanced for loop with an enum type, you have to use something like values() The expression Suspectvalues() stands for all the items you list in the declaration of the Suspect enum type So, in the loop of Listing 6-5, mySuspect becomes mustard, then plum, then green, and so on When you apply values() to the name of an enum type, you get an array of items belonging to that enum type To read all about arrays, see 11

ave you read or heard anything about objectoriented programming Sometimes, all the objectoriented programmers seem to belong to a little club They have a secret handshake, a secret sign, and a promise not to reveal object-oriented programming concepts to any outsiders Well, the secrecy is ending In this part, I take all the mystery out of object-oriented programming I introduce the concepts step by step and illustrate each concept with a Java program or two

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Thinking like a real object-oriented programmer Passing values to and from methods Hiding details in your object-oriented code

s a computer book author, I ve been told this over and over again I shouldn t expect people to read sections and chapters in their logical order People jump around, picking what they need and skipping what they don t feel like reading With that in mind, I realize that you may have skipped 1 If that s the case, please don t feel guilty You can compensate in just sixty seconds by reading the following information from 1: Because Java is an object-oriented programming language, your primary goal is to describe classes and objects A class is the idea behind a certain kind of thing An object is a concrete instance of a class The programmer defines a class, and from the class definition, the computer makes individual objects Of course, you can certainly choose to skip over the 60-second summary paragraph If that s the case, you may want to recoup some of your losses You can do that by reading the following two-word summary of 1: Classes; objects

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

What distinguishes one bank account from another If you ask a banker this question, you hear a long sales pitch The banker describes interest rates,