loop for input validation with strings in java

Question

This is my main method, I need a way to check if the input isn't a integer, for when they are Strings i can enter a value such as "12345" and it would still be a string. Although i am not sure how to differentiate between a string, which can be anything, versus something just a integer?

import java.math.*;
import java.text.DecimalFormat;
import java.io.*;
import java.util.*;


 public class labBookFortyEight
{
     public static void main(String[] args)
     { 
    String make = null;
    String model = null;
    String color = null;
    String lNum = null;
    int min = 0;
    int quarters = 0;

    Scanner myInput = new Scanner(System.in);

        while(make == null && model == null && color == null && lNum == null && min == 0 && quarters == 0)
        {
            System.out.println("Please enter make, model, color, lisense num and mins spent ");

              if (myInput.hasNext()) {
                  System.out.println("you entered make");
                make = myInput.nextLine();
              }
                if(myInput.hasNext()){
                    System.out.println("you entered model");
                  model = myInput.nextLine();
              }
              if (myInput.hasNext()) {
                  System.out.println("you entered color");
                color = myInput.nextLine();
              }
              if (myInput.hasNext()) {
                  System.out.println("you entered lNum");
                lNum = myInput.nextLine();
             }
            if(myInput.hasNextInt()){
                System.out.println("you entered mins spent");
                min = myInput.nextInt();
                myInput.nextLine(); //consumes newline char from nextLine
            }
            if(myInput.hasNextInt()){
                System.out.println("you enter quarters entered");
                quarters = myInput.nextInt();
            }
              else if (myInput.hasNext()) {
                System.out.println("Please enter a proper value");
                myInput.next();
              } else {
                System.err.println("No more input");
                System.exit(1);
              }
        }
                System.out.println("the values you entered are " + make + " " + model + " " + color + " " + lNum + " " + min);

Do you want the user to type an integer, and if none provided, ask him again until he provide one valid ? — NoDataFound
– NoDataFound, Commented Aug 10, 2014 at 14:25
Check out the following post for a few solutions: stackoverflow.com/questions/237159/… — Judah Schvimer
– Judah Schvimer, Commented Aug 10, 2014 at 17:22

ThreeFx · Accepted Answer · 2014-08-10 14:03:19Z

2

For this sort of thing you may need to look into regex or regular expressions which you can check if it matches.

String regex = "^[0-9]";
String data = "23343453";
System.out.println(data.matches(regex));

edited Aug 10, 2014 at 14:03

ThreeFx

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answered Aug 10, 2014 at 14:01

user3255780

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Comments

Bohemian · Accepted Answer · 2014-08-10 14:45:19Z

1

Use regex:

if (str.matches("\\d+"))

The regex \d+ means "one or more digits", and matches() only returns true if the whole String matches the regex.

edited Aug 10, 2014 at 14:45

answered Aug 10, 2014 at 14:39

Bohemian♦

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