how to find words within a range in a TreeSet<String> using regular expressions (java)

Question

I am iterating though a TreeSet and printing it out:

while (it.hasNext()) {
  System.out.println(it.next());
}

output:

after
explorers
giant
hoping
internet
into
.
.
.
virtual 
world

However, I would like to only print out those strings who's first character is within the range m-z. I have been playing around with java.util.regex, with no success:

String pattern = "[^m-z]";

Do I have the right idea here? Or is there a simpler way of doing this? All I want to do is make sure I only print out those Strings in the TreeSet who's first character is within the range m-z.

Answer 1

seems like an homework but anyhow, the "[^m-z]" means NOT m-z

try putting the "^" outside the "[]"

Have a look at the Pattern class and BTW, try String.matches()

Answer 2

First of all, your regular expression is wrong. You want

"^[m-z]"

Second of all, you don't show the code you're using to do the matching.

Third: If you're willing to do something besides regular expressions and iteration, you should look into SortedSet.tailSet. That's probably what your teacher wants.

Answer 3

I don't know about regular expressions, but you can easily find those Elements that begin with a letter from m-z:

wordSet.tailSet("m", true);

Usually you would use subSet() with the lower bound and the next character from the upper bound, but since z is the last character that can't easily be done.

For getting the set from 'b' to 'y' you'd do

wordSet.subSet("b", true, "z", false);

Answer 4

I agree this sounds suspiciously like homework, but here we go...

while (it.hasNext()) {
    String element = it.next();
    if (element.toLowerCase().matches("^[m-z].*")) {
        System.out.println(element);
    }
}

Answer 5

I know the original poster discussed using a regular expression, but maybe he had a problem to solve, decided to use regular expressions, and now has two problems to solve.

while (it.hasNext()) {
    String element = (String) it.next();
    char c = element.charAt(0);
    if (c >= 'm' && c <= 'z') {
        System.out.println(element);
    }
}

This seems to meet his requirement set out in bold in the original question, although it is possible his teacher dictated the use of regular expressions.

EDIT: I only bothered to read the full question just now. However, I still think it is valuable to understand that regular expressions aren't the only way to solve this problem.