calculate minimum value from user input while excluding loop termination number (-1)

Question

Hey I'm trying to work out the minimum and maximum value from user input while disregarding the loop terminated value, which is -1. I understand how to do everything except how to disregard -1 when calculating minimum value for the input. Here's the code I've got so far:

    int value = 0;
    int max = value;
    int min = max;

    Scanner scan = new Scanner(System.in);

    while (value != -1) {
        System.out.print("Value: ");
        value = scan.nextInt();
        if (min > value) {
        min = value;     }

       if (max < value) {
           max = value; }
    }

    System.out.println("Min = " + min);
    System.out.println("Min = " + min);

How can I calculate the minimum value while disregarding -1?

Thanks.

score 1 · Accepted Answer · answered Mar 30 '16 at 03:46

You turn the loop into a never-ending loop, and add a break when termination number is detected:

Scanner scan = new Scanner(System.in);

int max = Integer.MIN_VALUE;
int min = Integer.MAX_VALUE;
for (;;) { // never-ending loop
    System.out.print("Value: ");
    if (! scan.hasNextInt()) {
        System.out.println("** Invalid input **");
        scan.nextLine(); // discard invalid input
        continue; // loop back to prompt again
    }
    int value = scan.nextInt();
    if (value == -1) // termination number
        break;
    if (value < min)
        min = value;
    else if (value > max)
        max = value;
}
System.out.println("Min = " + min);
System.out.println("Max = " + max);

Also fixed:

Initialization of min and max (otherwise min will likely always be 0)
Validation of Scanner input (so program doesn't die with exception on bad input)
Printing of max (was printing min twice)
Indentation (so code structure is clearly visible to human readers)

any reason you use an empty for loop instead of a while(true) loop? I've seen both idioms and always figured it's probably just programmer preference. — Austin, Mar 30 '16 at 03:49
@AustinD It is entirely programmer preference. See http://stackoverflow.com/questions/8880870/java-for-vs-whiletrue — Andreas, Mar 30 '16 at 03:52

score 0 · Answer 2 · answered Mar 30 '16 at 03:40

Add if (value == -1) break; right before the line that starts withif (min > value). This causes the loop to break once the terminal (-1) character is read.

For clarity, you can then change your loop condition to while(true). This is a pretty common idiom for this situation.

calculate minimum value from user input while excluding loop termination number (-1)

2 Answers2