条件表达式：错误消息说明类型不完整

Question

I can't seem to figure this out. I feel like it so easy that I am missing it. I keep getting an error message saying incomplete types and pointing at the? What am I doing wrong?

Using a conditional expression, write a statement that increments numUsers if updateDirection is 1, otherwise decrements numUsers . Ex: if numUsers is 8 and updateDirection is 1, numUsers becomes 9; if updateDirection is 0, numUsers becomes 7.

Hint: Start with " numUsers =... ".

import java.util.Scanner;

public class UpdateNumberOfUsers {
   public static void main (String [] args) {
      Scanner scnr = new Scanner(System.in);
      int numUsers;
      int updateDirection;

      numUsers = scnr.nextInt();
      updateDirection = scnr.nextInt();
      String condStr; 
     
      condStr = (numUsers < 8) ? +1 : -1;

      System.out.println("New value is: " + numUsers);
   }
}

Answer 1

I give you only guidlines and not the complete answer as it looks like an exercice and it's better to do it by yourself.

Try to write the same line without a ternary operator:

if (numUsers < 8) {
    condStr  = +1;
} else {
    condStr = -1;
}

This code:

• never update the value of numUsers
• doesn't use the value of updateDirection
• uses incompatible values (a String set to -1 or +1 makes no sense)

The increment/decrement operators:

myVar++; 
myVar--;

The equivalent (Note the order of the operators):

myVar += 1;
myVar -= 1;

The complete form:

myVar = myVar + 1;
myVar = myVar - 1;

Now you need to use those operators to increment/decrement numUsers (so numUsers++; or numUsers--; ) according to the value updateDirection (the variable you need to use the if condition or in the ternary condition). There is no need for condStr in your code.

Answer 2

Thank you for the help and advice you both have given me. I was able to complete the assigment. This was the input I put in and everythign outputed perfectly. Thank you jhamon for not giving me the answer and making me use my brain and the guides you provided.

if (updateDirection >= 1) {
         numUsers += 1;
      }
      else {
         numUsers -= 1;
      }