如何使用 java 中的正则表达式匹配结尾括号？

Question

I have some pattern which i want to match using java regex.The pattern sometimes has brackets sometimes it does not have. Example of pattern:

Test string:      (2555.45)
Test string:      50.00
Test string:     2345,46.00

I have wrote the below program but somehow it does not take the ending parentheses when I tried to match.

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

public class Main {
    public static void main( String args[] ) {
    String re = ".*Test string:\\s+([^\\\\d]+\\d[.,]\\d+).*";
    Pattern p = Pattern.compile(re);

     List<String> inputs = Arrays.asList( "Test string:      (2555.45)", "Test string:      50.00", "Test string:     2345,46.00", "Test string:     620.26","Test string:     37687.20" );
//for (String s : arr) {
//    System.out.println(s.matches(re));
//}

inputs.forEach(in->{
     Matcher m = p.matcher(in);
   if (m.matches()) {
       System.out.println(m.group(1));
   }


});  


    }
}

What I might be missing here.Any clue will be helpful

Answer 1

The parenthesis ( ( and ) ), are special characters to the regular expression engine. To go around this, we escape them by adding an extra \ in front. Due to how Java works, we need to escape that extra \ again, so to match ( and ) in Java you would need to have \\( or \\) .

Since in your test case the parenthesis might or might not be there, I suggest you add a ? operator. I also noticed (unless I am missing something) that you are expecting to match 2 : characters as opposed to one.