Why cant i use this input variable? [duplicate]

Question

        float x = 12.1f;
        float y = 0.8f;
        float z = 9.81f;

        boolean key2 = false;
        while (!key2) {
            try {
                Scanner scanner2 = new Scanner(System.in);
                System.out.println("What is the velocity?: ");
                float TheNumber = scanner2.nextFloat();
                key2 = true;
            }//end of try
            catch(Exception e) {
                System.out.println("Thats not a number, try again");
            }// end of catch    
        }//end of while

float result = 2 + x + y + TheNumber + z;     // Why cant i use "TheNumber" variable ?

output: TheNumber cannot be resolved to a variable

Hey guys, im having a problem trying to use a variable inside the while loop, i come from Python so its all a little new for me, is there a reason i cant use variables? and if so, how could i use it?

Answer 1

TheNumber is scoped to the try block.
This question is very similar to this one - Why does a Try/Catch block create new variable scope? .
Also see this tutorial - https://www.baeldung.com/java-variable-scope

Answer 2

You have to define the variable outside the loop. If you define it inside the loop, then it only exists inside the loop. So try this:

float x = 12.1f;
float y = 0.8f;
float z = 9.81f;
float TheNumber;

boolean key2 = false;
while (!key2) {
    try {
        Scanner scanner2 = new Scanner(System.in);
        System.out.println("What is the velocity?: ");
        TheNumber = scanner2.nextFloat();
        key2 = true;
        }//end of try
    catch(Exception e) {
        System.out.println("Thats not a number, try again");
         }// end of catch    
}//end of while

float result = 2 + x + y + TheNumber + z;