REGEX to MATCH a given PREFIX and SUFFIX

Question

I have strings composed of:

• Prefix + Suffix (may contain spaces between them)
• Prefix is ALFA (variable in length, upper or lower case, may not be present)
• Suffix is NUMERIC (variable in length, may contain spaces)

I need a REGEX to MATCH a given ( variable ) PREFIX and SUFFIX

Examples (prefix=ABCD, suffix=123456789):

String to match (several possible combinations):  
ABCD123456789  
abcd123456789  
ABCD 123456789  
abcd 123456789  
ABCD 123 456 789  
abcd 123 456 789  
123456789  
123 456 789  

String matches
+--------+-------------------+-------+  
| PREFIX |      SUFFIX       | MATCH |  
+--------+-------------------+-------+  
|        | 123456789         | YES   |  
|        | 123 456 789       | YES   |  
|        | 1 2 3 4 5 6 7 8 9 | YES   |  
| ABCD   | 123 456 789       | YES   |  
| ABCD   | 1 2 3 4 5 6 7 8 9 | YES   |  
+--------+-------------------+-------+  
|        | 12345678          | NO    |  
|        | 123 456 7890      | NO    |  
| ABCD   | 12345678          | NO    |  
| ABCD   | 123 456 7890      | NO    |  
|        | 123456789 ABCD    | NO    |  
| AB     | 123456789         | NO    |  
+--------+-------------------+-------+  

In other words :
- Prefix must MATCH if present (case insensitive) and must be IGNORED if not present
- Suffix must MATCH (spaces must be IGNORED!)

Equivalent JAVA code would be:

//remove prefix (case insensitive)
STRING.substring(STRING.toUpperCase().startsWith(PREFIX) ? PREFIX.length() : 0).
//remove spaces
replace(" ","").
//match
equals(SUFFIX);

Thanks a lot.

Answer 1

Remove all spaces in/around the numeric suffix first:

str.replaceAll(" (?=[\\d ]*$)", "").matches("(?i)(ABCD)?123456789")

Matches all your test cases (and doesn't match your non-matches).

Answer 2

I know your question has a Java tag but I'm not familiar with Java. Since Java and JavaScript have some similarities, here is a JavaScript implementation to get ideas from.

 var rows = [{ prefix: null, suffix: '123456789', assert: true }, { prefix: null, suffix: '1123 456 789', assert: true }, { prefix: null, suffix: '1 2 3 4 5 6 7 8 9', assert: true }, { prefix: 'ABCD', suffix: '123 456 789', assert: true }, { prefix: 'ABCD', suffix: '1 2 3 4 5 6 7 8 9', assert: true }, { prefix: null, suffix: '12345678', assert: false }, { prefix: null, suffix: '123 456 7890', assert: false }, { prefix: 'ABCD', suffix: '12345678', assert: false }, { prefix: 'ABCD', suffix: '123 456 7890', assert: false }, { prefix: null, suffix: '123456789 ABCD', assert: false }, { prefix: 'AB', suffix: '123456789', assert: false }]; var PREFIX = 'ABCD'; var SUFFIX = '123456789'; var separator = '_'; var regex = new RegExp('^(' + PREFIX.toLowerCase() + ')?' + separator + '.*' + SUFFIX.replace(/\\s+/g, '') + '$', 'g'); document.write('<pre>generated regex: ' + regex + '</pre>'); for (var i = 0; i < rows.length; i++) { regex.lastIndex = 0; var item = rows[i]; var pre = (item.prefix || '').toLowerCase(); var suf = item.suffix.replace(/\\s+/g, ''); var subject = pre + separator + suf; var result = regex.test(subject); document.write('<pre class="' + ((result === item.assert) ? 'success' : 'fail') + '">' + pre + ' ' + suf + ', expected: ' + item.assert + ', result: ' + result + '</pre>'); } 

 pre { padding: 5px; } .success { border: 1px solid green; } .fail { border: 1px solid red; }