Input type checking in java

Question

I would like to know how to check an input type in java?

• If I input 23 it should say "The input is integer type"
• If 3.0 then "the input is float type"
• If Suman then "The input is string type" etc.

Answer 1

Using regex patterns and the built in Pattern class:

import java.util.Scanner;
import java.util.regex.Pattern;

public class TestClass {

    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();

        boolean containsDigit = Pattern.compile("[0-9]").matcher(input).find();
        boolean containsNonDigitNonPeriod = 
            Pattern.compile("[!--/:-~]").matcher(input).find();
        int numberOfPeriods = input.replaceAll("[^.]", "").length();

        if (containsDigit && !containsNonDigitNonPeriod)
        {
            if (numberOfPeriods > 1)
                System.out.println("A string has been input.");
            else if (numberOfPeriods == 1)
                System.out.println("A float has been input.");
            else 
                System.out.println("An integer has been input.");
        }
        else 
            System.out.println("A string has been input.");

        scanner.close();
    }
}