Regex: complex number

Question: This is my regex for imaginary number:

[0-9]{0,}\d\.[0-9]{0,}\d[i]|[0-9]{0,}\d[i]

      

        
        
        
      

    

It only accepts an imaginary number with a pure complex part.

When my parser is encountered, for example String im = "2i";

, it gets converted to String z = "complex(0, 2)" //complex(re, im)

- like this:

Matcher m = pattern.regex.matcher(exp);     //String exp = "2i + 5"

if(m.find())
{
  String key = m.group();                   //String key = "2i"
  int type = pattern.token;

   if(type == COMPLEX) 
   {
    key = key.replaceAll("i", "");          // key = "2"
    exp = m.replaceFirst("");               // exp = "5"
    exp = "complex(0," + key +")" + exp;    //exp = "complex(0,2) + 5"
   }

   return exp;
}

      

        
        
        
      

    

Is there any way to do this with a regex straight away? For example, any decimal number followed by the letter "i" is converted to another string - complex(0, number)

?