Using regex to define masks for numbers in Java

Question

I am trying to define a set of rules, that will compute a mask based on the number it is given. For example I am trying to return a mask of 8472952424 of any number that start with 12, 13, 14, Or return 847235XXXX for any number that starts with 7 or 8.

The input numbers are 4 digit Integers and the return is a String. Do I need to convert the integers to string before I do the regex on them, and I am also not sure how to construct the expressions.

Edit I have too much criteria to be done using separate if statements for each case. I am matching extension numbers to masks so it could be inserted correctly on Cisco CallManager database (in case you are curious)

Edit

This is what I have done for one of the cases but this is still not matching correctly:

public String lookupMask(int ext){
   //convert to String
   StringBuilder sb = new StringBuilder();
   sb.append(ext);
   String extString = sb.toString();

   //compile and match pattern
   Pattern p = Pattern.compile("^[12|13|14|15|17|19|42]");
   Matcher m = p.matcher(extString);
   if(m.matches()){
       return "8472952424";
   }
   return null;
}

http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html — nachokk, Jun 25 '13 at 15:19
I don't know if you need to convert them to a `String`. A four-digit integer that begins with 12, 13, or 14 would be `1200 <= x && x <= 1499`, right? It's hard to tell exactly what you're trying to do, and how (and why) you're constructing your masks. And why you think regex would be the best option (though, if you do need regexes for this, then yes, you need to convert to `String`). — Reinstate Monica -- notmaynard, Jun 25 '13 at 15:20

Mena · Accepted Answer · 2013-06-25T15:53:46.727

An example with Pattern could be this:

package test;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;

public class Main {
    // working Pattern
    private static final Pattern PATTERN = Pattern.compile("^((1[234579])|42)");
    // Your Pattern won't work because although it takes in account the start of the 
    // input, the OR within a character class does not exempt you to write round brackets 
    // around sequential characters such as "12". 
    // In fact here, the OR will be interpreted as the "|" character in the class, thus 
    // allowing it as a start character.
    private static final Pattern NON_WORKING_PATTERN = Pattern.compile("^[12|13|14|15|17|19|42]");
    private static final String STARTS_WITH_1_234 = "8472952424";
    private static final String STARTS_WITH_ANYTHING_ELSE = "847295XXXX";

    public static void main(String[] args) {
        // NON_WORKING_PATTERN "works" on "33333"
        System.out.println(NON_WORKING_PATTERN.matcher("33333").find());
        int[] testIntegers = new int[]{1200, 1300, 1400, 1500, 1700, 1900, 4200, 0000};
        List<String> results = new ArrayList<String>();
        for (int test: testIntegers) {
            if (PATTERN.matcher(String.valueOf(test)).find()) {
                results.add(STARTS_WITH_1_234);
            }
            else {
                results.add(STARTS_WITH_ANYTHING_ELSE);
            }
        }
        System.out.println(results);
    }
}

Output:

true
[8472952424, 8472952424, 8472952424, 8472952424, 8472952424, 8472952424, 8472952424, 847295XXXX]

Thanks, this works! how can I verify that my regex is right, is there a web tool that does it? I still have some other cases that I want to check — laitha0, Jun 25 '13 at 16:02
@user2247823 you're welcome. There are a number of Java and non-Java regex tester web apps online, just google it and you'll find plenty. Ultimately my personal bible is the official [Java SE 1.4.2 Pattern page](http://docs.oracle.com/javase/1.4.2/docs/api/java/util/regex/Pattern.html) — Mena, Jun 25 '13 at 16:07

Using regex to define masks for numbers in Java

1 Answers1