Extract number from string using regex in java

Question

I fail to extract a (double) number from a pre-defined input String using a regular expression.
The String is:

String inputline =\"Neuer Kontostand\";\"+2.11         


        

Answer 1

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

public class NumRegEx {

   public static void main( String[] args ) {
      String inputline = "\"Neuer Kontostand\";\"+2.117,68\"";
      Pattern p = Pattern.compile(".*;\"(\\+|-)?([0-9.,]+).*");
      Matcher m = p.matcher( inputline );
      if( m.matches()) { // required
         String sign  = m.group( 1 );
         String value = m.group( 2 );
         System.out.println( sign );
         System.out.println( value );
      }

   }
}

Output:

+
2.117,68

Answer 2

Pattern.compile("-?[0-9]+(?:,[0-9]+)?")

Explanation

-?        # an optional minus sign
[0-9]+    # decimal digits, at least one
(?:       # begin non-capturing group
  ,       #   the decimal point (German format)
  [0-9]+  #   decimal digits, at least one
)         # end non-capturing group, make optional

Note that this expression makes the decimal part (after the comma) optional, but does not match inputs like -,01.

If your expected input always has both parts (before and after the comma) you can use a simpler expression.

Pattern.compile("-?[0-9]+,[0-9]+")