CODEWITHSUNDEEP
javajava.util.scannersymbols
BennyElie
BennyElie

Reputation: 33

Using the percentage symbol as a user input in Java

If I want the user to input an interest rate in the format of : n% (n is a floating point number).

Given that % is not a valid number to be input, is there a way to nevertheless get the user input and then perform the necessary conversions?

Basically is there a way in which the following code can actually work:

import java.util.Scanner;

public class CanThisWork{

 public static void main(String[] args){

  Scanner input = new Scanner(System.in);
  System.out.println("Enter Annual Interest Rate");

  //user input is 5.4% for example

  //this is where the problem is because a double data type cannot contain the % symbol:
  double rate = input.nextDouble();

  System.out.println("Your Annual rate " + rate + " is an error");
 }
}

All jokes aside, I would love to get a solution to this predicament

Upvotes: 0

Views: 2942

Answers (3)

Ashishkumar Singh
Ashishkumar Singh

Reputation: 3600

Because 5.4% is not a Double, you would have to use Scanner methods that reads String as input like next or nextLine. But to can ensure that the String that is being read is a double ending with %, you can use hasNext(String pattern) method. 

if (input.hasNext("^[0-9]{1,}(.[0-9]*)?%$")) {
        String inputString = input.next();
        double rate = Double.parseDouble(inputString.substring(0, inputString.length() - 1));
        System.out.println("Your Annual rate " + rate + " is an error");
    }

   // Pattern explanation 
   ^ - Start of string
   [0-9]{1,} - ensure that at least one character is number
   [.[0-9]*]* - . can follow any number which can be followed by any number
   %$ - ensure that string must end with %

Above code will ensure that only Double number ending with % are passed through

Upvotes: 2

BHAWANI SINGH
BHAWANI SINGH

Reputation: 729

Since your input is not a double anymore you can't use input.nextDouble() instead, you need to get it as a string, replace the '%' and then parse it as a double.

double rate = Double.parseDouble(input.nextLine().replace("%",""));

Upvotes: 1

Mesalcode
Mesalcode

Reputation: 140

I would go with:

    public static void main(String[] args) {
     // TODO code application logic here
    Scanner input = new Scanner(System.in);
      System.out.println("Enter Annual Interest Rate");

      //user input is 5.4% for example

      //this is where the problem is because a double data type cannot contain the % 
      symbol:

      String userInput = input.nextLine(); // "5.4%"

      double percentage = Double.parseDouble(userInput.replace("%", "")) / 100; // 0.54
      //You can now do calculations or anything you want with this value.

     //multiplying it with 100 to get it to % again
      System.out.println("Your Annual rate " + percentage*100 + "% is an error");
}

Upvotes: 1

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