Making Multiple Choices with the SELECT CASE Statement in Java

Generator Denso QR Bar Code in Java Making Multiple Choices with the SELECT CASE Statement

computer to choose from three or more commands (or blocks of commands), the SELECT CASE (switch) statement may be easier to read and write instead Branching simply gives the computer multiple options to use when running By accepting outside information and comparing its value, a branching statement can help the computer choose an appropriate response out of many possible responses

Looping a fixed number of times with a FOR-NEXT loop Looping zero or more times with a WHILE loop Looping at least once with a DO loop Playing around with nested loops Exiting prematurely from a loop Examining your loops

o write any program, you must specify what the computer needs to do at any given time Sometimes, you may need to write the same command multiple times For example, suppose you want to print your name five times You could just write the same command five times like this:

Writing the same five commands is cumbersome Even worse, what if you suddenly decide you want to print your name not just five times, but five thousand times Do you really want to write the same command five thousand times Probably not, which is why computer scientists invented loops A loop is just a shortcut for making the computer run one or more commands without writing those commands multiple times So rather than type the same command five times as in the preceding example, you could use a loop like this:

This tells the computer to run the PRINT John Smith command five times If you want to print John Smith five thousand times, you just have to change the number of times you want the loop to run by replacing the 5 with 5000, such as

Loops basically make one or more commands run more than once, as shown in Figure 5-1

The simplest loop runs one or more commands a fixed number of times, such as five or ten times Such loops that run a fixed number of times are FOR-NEXT loops and look like this:

The first line serves two purposes The first time the FOR-NEXT loop runs, this line sets the value of the variable to an initial value, such as 1 The second and all additional times the FOR-NEXT loop runs, it checks if its

variable is still within a range of values, such as between 1 and 10 If so, the FOR-NEXT loop runs again The second line consists of one or more commands that you want to run multiple times The third line tells the FOR-NEXT loop to increase the value of its variable by 1 and run the FOR-NEXT loop again The FOR-NEXT loop defines four items: A variable The initial value of the variable (usually 1) The ending value of the variable One or more commands that run multiple times Repeating Commands by Looping

Like all variables, the name of a FOR-NEXT loop variable can be anything, although it s best to use a descriptive name if possible So if you want to print the names of all the employees of a company by using a FOR-NEXT loop, you could use EmployeeID as a descriptive variable name, such as

This example would print out each name (EmployeeName) starting with the employee who has the EmployeeID of 1 and continuing until it prints the employee with the EmployeeID of 150 If your FOR-NEXT loop variable is meant only for counting and doesn t represent anything, like employee numbers, you can just use a generic variable name, such as I or J, such as

This FOR-NEXT loop just prints the name John Smith on-screen 15 times Never change the value of a FOR-NEXT loop s variable within the loop or else you risk creating an endless loop the computer keeps running the same commands over and over again without stopping This makes your program appear to freeze or hang, essentially stopping your program from working altogether The following example creates an endless loop: