How can I print the largest number encountered in a loop?

Question

I am prompting the user for a series of numbers and want to keep track of the largest one entered and print that out at the end. Example:

Please enter a number (enter -1 to quit): 10

Enter your next number (-1 to quit): 7

Enter your next number (-1 to quit): 15

Enter your next number (-1 to quit): 11

Enter your next number (-1 to quit): -1

The largest number entered was 15

How do I print this largest number? Here is what I have tried:

int a;

while(true){
    System.out.print("Please enter a number (enter -1 to quit):");
    a = user.nextInt();
    if (a==-1) 
    {
        System.out.println("The largest number is the "+ );
        break;
    }
}

Keep track of the max number you have encountered on every loop, then just print it — gtgaxiola
– gtgaxiola, Commented Nov 10, 2014 at 16:20
Please explain about your idea on how to implement it first. — Venugopal Madathil
– Venugopal Madathil, Commented Nov 10, 2014 at 16:23

AdamMc331 · Accepted Answer · 2014-11-10 16:33:13Z

3

You should store a variable outside the loop that you change when needed.

Typically, you would set this number equal to the first value, but for this case, you can set it to -1 since that is not something that will change. Try this:

int maxNumber = -1;
while(true){
   System.out.print("Please enter a number (enter -1 to quit):");
   a = user.nextInt();
   if(a != -1 && a > maxNumber){
      maxNumber = a;
   else if(a == -1){
      // You can do a check here to be sure they even entered a number.
      if(maxNumber == -1){
         System.out.println("No number was input.");
      } else{
         System.out.println("The max number was " + maxNumber);
      }
   }
}

EDIT for further explanation

What this will do is check that if the user has entered a number that is larger than anything entered yet. If it is, it will change the value to that number. Example: If I type 2, and then 3, maxNumber will become 3. If I type in 0, max number will remain 3. If at any point I type -1, it will break as you have set up already.

EDIT 2

As far as what I meant when I said 'you would set this number equal to the first value' let me explain.

A user can input any value, except -1. So, how do I set the initial max value? If I say maxNumber = 0 and you enter nothing but negatives, I will print 0 as the max number when I am done. That being said, what I have done above is still not fool proof. If the user enters values only less than -1, I still will print an incorrect max. So, it would be best practice to get the first input value, and set that to your max, and change it if a new one is encountered. It would change the code to look like this:

int maxNumber = -1; // Just a junk value to start.
boolean firstNumber = true;
while(true){
   System.out.print("Please enter a number (enter -1 to quit): ");
   a = user.nextInt();
   if(a == -1 && firstNumber){ // If the user enters -1 right away.
      System.out.println("No number was input.");
   } else if(a == -1 && !firstNumber){ // If they've entered -1 after inputting a valid number
      System.out.println("The max number was " + maxNumber);
   } else{ // They've entered a valid number.
      if(firstNumber){ // If this is the first number, we set the max initially, and change this flag to false now.
         maxNumber = a;
         firstNumber = false;
      } else{ // Not first number, so only check if the input is larger.
         if(a > maxNumber){
            maxNumber = a;
         }
      }
   }
}

edited Nov 10, 2014 at 16:33

answered Nov 10, 2014 at 16:21

AdamMc331

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4 Comments

Bathsheba Over a year ago

int maxNumber = -1; is clumsy. +1 if you do this in a cuter way.

AdamMc331 Over a year ago

@bathsheba agreed, was in the middle of editing while you commented. Was thinking on the fly with -1.

Bathsheba Over a year ago

I don't like it since you can get bugs when the mandate of the function creeps to include negative inputs.

AdamMc331 Over a year ago

@Bathsheba what do you mean?

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