How to tell if an unknown number is in a String?

Question

I have an if statement which checks if a variable is equal to some string. But, I want to check if there is an number in the string, too. Something like this:

if(thestring.equals("I, am awesome. And I'm " + Somehowgetifthereisanumberhere + " years old")) {
    //Do stuff
}

Or more specifically, where x is the unknown number, just to know there is a number (any number) there:

String str = item.substring(item.indexOf("AaAaA" + x), item.lastIndexOf("I'm cool."));

How to do that?

Looked in SO..I think this has been asked: http://stackoverflow.com/questions/372148/regex-to-find-an-integer-within-a-string — Menelaos, May 21 '13 at 18:47

score 5 · Accepted Answer · edited May 21 '13 at 18:46

5

Use a regular expression:

if(thestring.matches("^I, am awesome. And I'm \\d+ years old$")) {
    //Do stuff
}

edited May 21 '13 at 18:46

user

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answered May 21 '13 at 18:39

Cairnarvon

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Also note that the double backslash is because the double backslash \\ translates to a single backslash within the string, and then the sequence \d is seen and parsed by the regular expression engine. – user May 21 '13 at 18:42
That's awesome, but can I somehow put this in my substring thing? Really thankful for your help :) – GuiceU May 21 '13 at 18:44
@GuiceU You don't; this would replace your `thestring.equals()` call. – user May 21 '13 at 18:45
@MichaelKjörling Yes, I know. So I cannot use this somehow in my substring? Is there anything else I can use then? EDIT: Or could'nt I just use the \\d+? – GuiceU May 21 '13 at 18:48
@GuiceU \\d+ (actually, \d+ - see my comment above about the double backslash) is regular expression syntax, so no, you cannot use it with `String.equals()`. However, you *can* use it with `String.matches()` as Cairnarvon showed in the answer. It *is* possible to do this without regular expressions, but I'd say they are by far the best suited tool for this kind of string processing. – user May 21 '13 at 18:50
The regex pattern \d matches any digit, and + means repeat the previous pattern for as long as possible (otherwise you'd match only a single digit). There's more to it than that if you dig into it all, but that's the gist of it. So by having \d+ in the match expression you will match one or more digits in that position, which is what you wanted to do. – user May 21 '13 at 18:52
@MichaelKjörling Dude, _thank you_! Seriously, you're awesome. Now to the question. Okey, I get that, so it isn't possible to use it with 'String.indexOf()' either? If not I'll just have to find another way to do this, but again. Thank you :) – GuiceU May 21 '13 at 19:24
@GuiceU If you need the position within the string as well, [Penelope's answer](http://stackoverflow.com/a/16677427/486504) is probably the best way to do it. But that wasn't in the original question. Also, you may want to try [searching for questions tagged java regex](http://stackoverflow.com/questions/tagged/java+regex). – user May 21 '13 at 19:31
@MichaelKjörling Well, doesn't work in my case. But thank you all anyway! – GuiceU May 22 '13 at 18:30

score 2 · Answer 2 · edited May 23 '17 at 11:57

2

You can use the regular expression.

Pattern pattern = Pattern.compile(".*[^0-9].*");

References:

edited May 23 '17 at 11:57

Community

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answered May 21 '13 at 18:41

Menelaos

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Penelope The Duck · Answer 3 · 2013-05-21T19:23:38.217

This regex should find any one, two or three digit number (in case they are 102 years old) within any string:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class TestClass {

public static void main(String[] args) {
    Pattern p = Pattern.compile("\\d\\d?\\d?");
    Matcher m = p.matcher("some string with a number like this 536 in it");
    while(m.find()){
        System.out.println(m.group());  //This will print the age in your string
        System.out.println(m.start());  //This will print the position in the string where it starts
    }
  }
}

Or this to test the entire string:

Pattern p = Pattern.compile("I, am awesome. And I'm \\d{1,3} years old");  //I've stolen Michael's \\d{1,3} bit here, 'cos it rocks.
Matcher m = p.matcher("I, am awesome. And I'm 65 years old");
    while(m.find()){
        System.out.println(m.group());
        System.out.println(m.start());
}

Michael - Sweet! Didn't realise you could do that. I've still got training wheels on. lol :-) — Penelope The Duck, May 21 '13 at 18:59

score 1 · Answer 4 · edited May 23 '17 at 12:11

1

You'd want to use regular expressions. See - Using Regular Expressions to Extract a Value in Java

To match letters 'd', 'e', or 'f', for e.g.:

[a-z&&[def]]

And also - Lesson: Regular Expressions

Pattern class is good study too

edited May 23 '17 at 12:11

Community

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answered May 21 '13 at 18:39

Caffeinated

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How to tell if an unknown number is in a String?

4 Answers4