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copied!<p>Your regex isn't quite right.</p> <p>When you write: <code>[RQrq1-6]*</code></p> <p>You're saying match zero or more repetitions of any character in the square brackets...</p> <p>Try this <code>[RQrq1-6]</code> - which means match exactly one.</p> <p>I wrote a little "spike" program:</p> <pre><code>import java.util.regex.Pattern; public class Spike { public static void main(String[] args) { testIt("Q"); testIt("q"); testIt("z"); testIt("Z"); testIt("R"); testIt("r"); testIt("0"); testIt("1"); testIt("2"); testIt("3"); testIt("4"); testIt("5"); testIt("6"); testIt("7"); testIt("02"); testIt("11"); testIt("17"); testIt(""); // should fail, used to pass with the question's regex } public static void testIt(String sample) { System.out.print(sample+" "); if (Pattern.matches("[RQrq1-6]*", sample)) { System.out.println("match"); } else { System.out.println("fail"); } } </code></pre> <p>}</p> <p>Output was this:</p> <pre><code>Q match q match z fail Z fail R match r match 0 fail 1 match 2 match 3 match 4 match 5 match 6 match 7 fail 02 fail 11 match 17 fail match </code></pre> <p>Having removed the star in the regex:</p> <pre><code>Q match q match z fail Z fail R match r match 0 fail 1 match 2 match 3 match 4 match 5 match 6 match 7 fail 02 fail 11 fail 17 fail fail </code></pre> <p>How to ignore the blanks</p> <p>Substitute this version of testit:</p> <pre><code>public static void testIt(String sample) { System.out.print(sample+" "); Pattern pattern = Pattern.compile("\\s*([RQrq1-6])\\s*"); Matcher matcher = pattern.matcher(sample); if (matcher.matches()) { System.out.println("match '"+matcher.group(1)+"'"); } else { System.out.println("fail"); } } </code></pre> <p>Here are the critical lines of the output: </p> <pre><code>testIt(" 6");// ignore space tests testIt(" 7");// ignore space tests testIt("6 ");// ignore space tests testIt("7 ");// ignore space tests 6 match '6' 7 fail 6 match '6' 7 fail </code></pre> <p>It uses a concept called a "capture group". A capture group is a section of a regex which is assigned a number so that the specific string of symbols that matched can be extracted. We're using a capture group here to pull the symbol out from the optional whitespace.</p>

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