while loop question

[anthony dwizzledorf]

I am just startin out with programming so bare with me. I wrote a simple program that allows a user to enter an amount of money and it will output an amount in change. I was wondering how I would incorporate a loop so that a user has the option of inputing a yes or no statement if they want to keep using the body of the program over and over again. Any
suggestions?

[Craig Wood]

Use a while loop with a boolean condition and ask the user on each iteration if they would like to continue.

    boolean keepGoing = true;
    while(keepGoing)
    {
        money changing code...
        get user input here with JOPtionPane message dialog or
        via the command line input to set the current value of
        keepGoing for the next iteration
    }

[anthony dwizzledorf]

Thanks Craig. I'll give it a shot.

[Dirk Schreckmann]

Welcome to JavaRanch, anthony!
As you're new around these parts and have asked a good beginner's type question, allow me to recommend the following list of resources that you might find useful to have around.

Sun's Java Tutorial

Introduction to Computer Science using Java by Bradley Kjell

Introduction to Programming Using Java by David J. Eck

Dick Baldwin's Java Programming Tutorials

Interactive Programming In Java by Lynn Andrea Stein

Bruce Eckel's Thinking In Java

JavaRanch's own Campfire Stories

Allen B. Downey's How To Think Like A Computer Scientist

Also, when you start to make use of the standard Java libraries a bit more, you'll likely find the API documentation nice to reference to learn just what things can do and how they do it.
[ March 02, 2004: Message edited by: Dirk Schreckmann ]

[sever oon]

Not to nitpick , but the only difference between the do/while and the while/repeat loop is that the do/while is guaranteed to run the loop body at least one time before exiting:

boolean goAgain = false;
while( goAgain ) {
  // do something
}
do {
  // do something else
} while( goAgain );

The "do something else" is the only code that will run, and it will only run once in the above example. Since that's the only purpose for the do loop's existence, and you meet the criteria, I say give that poor do loop its shot at the limelight (it gets used so infrequently). You may want to consider defining your exit criteria according to a bunch of exit constants, that way you can have the program exit with information about why it's exiting:

public class Program {
  public static final int EXECUTE_ITERATE = 1;
  public static final int EXIT_NORMAL = 0;
  public static final int EXIT_IMPROPER_USAGE = -1;
  public static final int EXIT_CORRUPT_DATA = -2;
  // ...
  public static void main( String[] args ) {
    int exitCode = Program.EXECUTE_ITERATE;
    do {
      // main body
      if( /* time to exit */ ) {
        exitCode = // one of the exit codes...
      }
    } while( exitCode == Program.EXECUTE_ITERATE );
    System.exit( exitCode );
  }
}

sev
[ March 03, 2004: Message edited by: sever oon ]