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Thread: Need help with this nested loop

  1. #1
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    Default Need help with this nested loop

    This is a piece of code from a project I'm working on that prompts the user to pick a number of students between 1 and 10, and a score between 1 and 100 for each of the n number of students. If the user inputs a number of students or a score that is out of the range, an error message pops up and they will be prompted to input this/these bad value(s) again.

    Picking the number of students is simple enough, and the code here works perfectly fine, mostly because it doesn't involve a loop to check the value (only 1 int).

    The "scores" portion of the code (beginning with scores = new double[]) must have a boolean named errFlag that controls the while loop, an inner for loop, and if/else if statements. This code works as well, but the inner "for" loop causes the error in the "else if" statement:

    System.out.println("ERROR: Enter number(s) in the range of 0-100!");
    System.out.println("ERROR: Enter all " + (numStudents) + " scores again: ");

    to print as many times as numStudents (ie 2 students inputted, error lines print twice). I only want this error to print once if any of the values inputted are out of bounds (1-100). Is there any way I can control the loop to only print this error out once no matter how many times the loop executes?



    boolean errFlag = false;
    final int MIN = 0;
    final int MAX = 100;
    final int MAX_STUDENTS = 10;
     
    do{
     //prompt user for number of students between 1 and 10
     System.out.print("Enter number of students(");
     System.out.println((MIN + 1) + "-" + (MAX_STUDENTS + "): "));
     numStudents = scan.nextInt();
     //keep prompting user for number of students until they pick one between 1 and 10
    if(numStudents > MAX_STUDENTS)
     {
       do {
         System.out.println("Error: Enter an integer in the range of 1-10!");
         System.out.print("Enter number of students(");
         System.out.println((MIN + 1) + "-" + (MAX_STUDENTS + "): "));
         numStudents = scan.nextInt();
       }while(numStudents > MAX_STUDENTS);
     }
     
    //prompt the user for scores for each of these students until all five are between 1 and 100
       scores = new double[numStudents];
       System.out.print("Enter " + (numStudents) + " scores(");
       System.out.println((MIN) + "-" + (MAX + "): "));
       while(errFlag = false);
       {
         for(int i = 0; i < numStudents; i++)
             {
           tmp = scan.nextDouble();
           if(tmp >= MIN && tmp <= MAX)
           {
             scores[i] = tmp;
             errFlag = true;
           }
           else if(tmp < MIN || tmp > MAX)
           {
             System.out.println("ERROR: Enter number(s) in the range of 0-100!");
             System.out.println("ERROR: Enter all " + (numStudents) + " scores again: ");
             i--;
             errFlag = false;
           }
         }
       }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Need help with this nested loop

    Is there any way I can control the loop to only print this error out once no matter how many times the loop executes?
    Use a boolean variable. If it is initially true, execute the code to do the print and then set its value false for the next time around the loop.
    boolean oneTime = true;
    ...
    // inside loop
    if(oneTime) {
      oneTime = false;  // turn off for next time
      //  do the one time stuff
    } // end if(oneTime)
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Need help with this nested loop

    Sorry for the late response Norm, this did in fact fix the issue I had, and I thank you!

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