Generate fixed length Strings filled with whitespaces

Question

I need to produce fixed length string to generate a character position based file. The missing characters must be filled with space character.

As an example, the fi

Answer 1

Here's a neat trick:

// E.g pad("sss","00000000"); should deliver "00000sss".
public static String pad(String string, String pad) {
  /*
   * Add the pad to the left of string then take as many characters from the right 
   * that is the same length as the pad.
   * This would normally mean starting my substring at 
   * pad.length() + string.length() - pad.length() but obviously the pad.length()'s 
   * cancel.
   *
   * 00000000sss
   *    ^ ----- Cut before this character - pos = 8 + 3 - 8 = 3
   */
  return (pad + string).substring(string.length());
}

public static void main(String[] args) throws InterruptedException {
  try {
    System.out.println("Pad 'Hello' with '          ' produces: '"+pad("Hello","          ")+"'");
    // Prints: Pad 'Hello' with '          ' produces: '     Hello'
  } catch (Exception e) {
    e.printStackTrace();
  }
}