Java bug? Different output on 2 identic regex's

Question

My regular expression has 2 different outputs from the same code... but i don't know what's wrong. Here's a piece of code, i hope you can help me. Thanks!

String s = "48° 18′ 13,94″ nördliche Breite, "
         + "11° 34′ 31,98″ östliche Länge";

String kommazahl = "[0-9]{1,2}([\\.,][0-9]+)?";
String zahl = "[0-9]{1,2}";

Pattern p1 = Pattern.compile("("+ zahl +"[°/| ]{1,2}"+ zahl +"(['′/| ]{1,2}("+ kommazahl +")?)?).*"
                            +"("+ zahl +"[°/| ]{1,2}"+ zahl +"(['′/| ]{1,2}("+ kommazahl +")?)?).*");

Matcher m1 = p1.matcher(s);

System.out.println(m1.group(1) + "\n" + m1.group(5));

// Output should be:
// 48° 18′ 13,94
// 11° 34′ 31,98

// Output is:
// 48° 18′ 13,94
// 1° 34′ 31,98

Why do so many people assume its a bug in the language rather than checking their own code more closely? — z -
– z -, Commented Jun 5, 2009 at 13:19
zahl seems to be wrong - degrees can have 3 digits. That has nothing to do with your problem, it may just be a bug. — Tobias Langner
– Tobias Langner, Commented Jun 5, 2009 at 13:56
Please pay attention to the suggest prompts when tagging your question. Any tag with a number less than 10 after it's name is probably wrong. — Joel Coehoorn
– Joel Coehoorn, Commented Jun 5, 2009 at 14:30

laalto · Accepted Answer · 2009-06-05 13:21:15Z

5

The .* matches the first 1 of 11 greedily, while still allowing the rest of the pattern to match. Replace .* with something like [^0-9]*.

answered Jun 5, 2009 at 13:21

laalto

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Jon Skeet · Accepted Answer · 2009-06-05 13:18:00Z

4

The problem is the .* at the end of the first line of the pattern. That's greedily matching "nördliche Breite, 1".

Perhaps you should change it to capture ".*, " so that it knows when to stop?

Pattern p1 = Pattern.compile
    ("("+ zahl +"[°/| ]{1,2}"+ zahl +"(['′/| ]{1,2}("+ kommazahl +")?)?).*, "
    +"("+ zahl +"[°/| ]{1,2}"+ zahl +"(['′/| ]{1,2}("+ kommazahl +")?)?).*");

Of course, that will only work if there's always a "comma space" between the two values you want in the rest of your data.

answered Jun 5, 2009 at 13:18

Jon Skeet

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