Apex Regex Extract Numeric Value from String

Question

B"H
I am unable to extract a consecutive set of numbers from within a (single line) string using ([0-9]+). However, surrounding it with match-all other does work (.*?[0-9].*). Can someone explain to me why ([0-9]+) is not working for this task.
Here's my code:

@Test
public void testMethod(){
    Pattern pat = Pattern.compile("([0-9]+)");
    Matcher matcher = pat.matcher("red fox 11133434 red fox");
    Boolean matches = matcher.matches();
    Assert.assertTrue("find numbers within string", matches);
    Assert.assertEquals("11133434", matcher.group(1));
}

dzh · Answer

Here's a utility method with a corresponding test class
    /**
     * @param input string that contains any number
     *
     * @return first digits found in string, null if input blank, found no match or too large for integer
     */
    public static Integer getInteger(String input){
        if(String.isEmpty(input)){
            return null;
        }
        Matcher matcher = Pattern.compile('\d+').matcher(input);
        if(matcher.find()){
            try {
                return Integer.valueOf(matcher.group(0));
            } catch(Exception e){
                System.debug(LoggingLevel.ERROR, e);
                return null;
            }
        } else {
            return null;
        }
    }

Test
@IsTest
static void getInteger(){
    System.assertEquals(
            1234567890,
            Strings.getInteger('foo 1234567890')
    );
    System.assertEquals(
            200,
            Strings.getInteger('-200')
    );
    System.assertEquals(
            1234567890,
            Strings.getInteger('1234567890 foo')
    );
    System.assertEquals(
            1234567890,
            Strings.getInteger('1234567890')
    );
    System.assertEquals(
            1234567890,
            Strings.getInteger('1234567890.321')
    );
    System.assertEquals(
            1234567890,
            Strings.getInteger('    1234567890   ')
    );
    System.assertEquals(
            1234567890,
            Strings.getInteger('baz 1234567890 foo 321')
    );
    System.assertEquals(
            null,
            Strings.getInteger('baz 1234567890123456789012345678901234567890')
    );
    System.assertEquals(
            null,
            Strings.getInteger('give potato')
    );
    System.assertEquals(
            null,
            Strings.getInteger('')
    );
    System.assertEquals(
            null,
            Strings.getInteger(null)
    );
}

Yossi Cadaner · Answer

B"H
Thanks Eric for answering the question. Just for completeness I am sharing the definition difference between find and matches from the Java docs:

A matcher is created from a pattern by invoking the pattern's matcher method. Once created, a matcher can be used to perform three different kinds of match operations:

The matches method attempts to match the entire input sequence against the pattern.
The lookingAt method attempts to match the input sequence, starting at the beginning, against the pattern.
The find method scans the input sequence looking for the next subsequence that matches the pattern.

Eric · Answer

You are using a capturing group so this works as you expect: (You need to use find):

Pattern pat = Pattern.compile('([0-9]+)');
    Matcher matcher = pat.matcher('red fox 11133434 red fox');
    Boolean matches = matcher.find();
    system.debug(logginglevel.error,matches);
    system.debug(logginglevel.error,matcher.group(1));

You will notice the debugs are true and 11133434

A good site to test out your regex and break it down it:

https://regex101.com

Apex Regex Extract Numeric Value from String

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