number out of string in java

Question

I have something like "ali123hgj". i want to have 123 in integer. how can i make it in java?

Answer 1

int i = Integer.parseInt("blah123yeah4yeah".replaceAll("\\D", ""));
// i == 1234

Note how this will "merge" digits from different parts of the strings together into one number. If you only have one number anyway, then this still works. If you only want the first number, then you can do something like this:

int i = Integer.parseInt("x-42x100x".replaceAll("^\\D*?(-?\\d+).*$", "$1"));
// i == -42

The regex is a bit more complicated, but it basically replaces the whole string with the first sequence of digits that it contains (with optional minus sign), before using Integer.parseInt to parse into integer.

Answer 2

Use the following RegExp (see http://java.sun.com/docs/books/tutorial/essential/regex/):

\d+

By:

final Pattern pattern = Pattern.compile("\\d+"); // the regex
final Matcher matcher = pattern.matcher("ali123hgj"); // your string

final ArrayList<Integer> ints = new ArrayList<Integer>(); // results

while (matcher.find()) { // for each match
    ints.add(Integer.parseInt(matcher.group())); // convert to int
}