CODEWITHSUNDEEP
java
Vico Pelaez
Vico Pelaez

Reputation: 51

Verify if user has entered valid data type

I want to check that the data entered by the user via terminal is the correct type needed in the program. If it is not, the code should loop so it asks for the data again before proceeding to the next step.

Example:

The message in terminal is as follows:

Enter Number:

and the user enters a string such as

yes

How can I loop the program and ask for the number again until the user enters a number of type double?

The code so far for this is:

System.out.println("Enter number:");
double number = scanner.nextDouble();

Upvotes: 0

Views: 2883

Answers (2)

Reimeus
Reimeus

Reputation: 159874

As you're using Scanner, you could use Scanner.hasDouble(). To ensure that you do get a valid double, some looping mechanism will be necessary: 

boolean numberFound = false;
while (!numberFound) {
   if (input.hasNextDouble()) {
    number = input.nextDouble();
    numberFound = true;
   } else {
    System.out.println("Invalid double " + input.next());
   }
}

Upvotes: 1

Juvanis
Juvanis

Reputation: 25950

double number;

try
{
   number = scanner.nextDouble();
   number = parseDouble(inputString);
}
catch(NumberFormatException nfe)
{
   System.out.println("Please enter a valid double!");
   number = scanner.nextDouble();
   number = parseDouble(inputString);
   // if the input is not valid again, you need a loop, rethink.
}

Upvotes: 1

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