How to check if the input string from Scanner Util matches an initial string

Question

So currently I have a setup where users enter a number from scanner util and I have a boolean that checks if the string entered is 4 digits and is only digits how can I create a boolean that would check it compared to another string for instance:

String pin = "6357";

what type of boolean would I have to compare the string to the one entered by user. Here is my current code checking the length go the string:

import java.security.MessageDigest;
import java.util.Scanner;

public class pin
{

public static void main( String[] args ) {
    Scanner kbd = new Scanner( System.in );
    String      pin;
    System.out.print( "Enter pin: " );
    pin = kbd.next();
    System.out.println( "Valid: " + isValid(pin) );
    System.out.println( "Is int: " + isInt(pin) );
    System.out.println( "MD5: " + md5HexString(pin) );
}

public static boolean isInt( String s ) {
    try {
        int i = Integer.parseInt( s );
        System.out.println( "Int: " + i );
        return true;
    }
    catch( Exception ex ) {
        return false;
    }
}

public static boolean isValid( String s ) {
    return s.matches( "\\d{4}" ); // must be 4 digits long
}

As can be seen this does not compare it to another existing string so what if I had something like this:

import java.security.MessageDigest;
import java.util.Scanner;

public class pin
{
   String pinnum = "6357";

public static void main( String[] args ) {
    Scanner kbd = new Scanner( System.in );
    String      pin;
    System.out.print( "Enter pin: " );
    pin = kbd.next();
    System.out.println( "Valid: " + isValid(pin) );
    System.out.println( "Is int: " + isInt(pin) );
    System.out.println( "MD5: " + md5HexString(pin) );
}

public static boolean isInt( String s ) {
    try {
        int i = Integer.parseInt( s );
        System.out.println( "Int: " + i );
        return true;
    }
    catch( Exception ex ) {
        return false;
    }
}

public static boolean isValid( String s ) {
    //what to put here?
}

In this example I pre set up a pin that I would like to check if what the user entered through scanner util matches exactly. Is this possible?

Just note `isInt` is not necessary you can just use `isValid` to check if the input is a valid integer or not — Youcef LAIDANI, Apr 21 '18 at 18:10
Note also that the sharp in the end of `ping#` illegal character in java! — Youcef LAIDANI, Apr 21 '18 at 18:13
In the second piece of code you also don't need to check `isInt`! — Youcef LAIDANI, Apr 21 '18 at 18:14
@YCF_L ahh yes thanks for pointing that out I just changed it and I did not think through the ending of # — , Apr 21 '18 at 18:14

score 1 · Accepted Answer · edited Apr 21 '18 at 18:16

1

you could use the .equals() method to comapare two values to see if they match.

pinnum.equals(s)

a more detailed explanation can be found here: How do I compare strings in Java?

edited Apr 21 '18 at 18:16

Youcef LAIDANI

55,661
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answered Apr 21 '18 at 18:12

Connor J

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i just left it there to show that its the user entered pin and not the hardcoded pin - but yeah you are right - shouldn't use those characters! – Connor J Apr 21 '18 at 18:17
Thanks for the code and thanks for whoever left the link too will check that out for more since I will be expanding more later! – Apr 21 '18 at 18:18

score 1 · Answer 2 · answered Apr 21 '18 at 18:20

1

If you are really working on validations, for the sake of Single Responsibility (SOLID Principles) it is better to have this kinds of validation things in another class. In this case you can use .equals() method.

answered Apr 21 '18 at 18:20

raydex

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How to check if the input string from Scanner Util matches an initial string

2 Answers2