public static void main(String[] args) throws IOException
{
String test = "ab19198zxncvl1308j10923.";
StringBuilder result = new StringBuilder();
test.chars().mapToObj( i-> (char)i ).filter( c -> Character.isDigit(c) || c == '.' ).forEach( c -> result.append(c) );
System.out.println( result ); //returns 19198.130810923.
}