code: public final int stringWidth(String text) {
  		int		stringWidth = 0;
  
  		if (!LwjgFontUtil.isEmpty(text)) {
  			for (int i = 0; i < text.length(); i++) {
  				char				ch = text.charAt(i);
  				MappedCharacter	character = getMappedCharacter(ch);
  
  				if (character == null) {
  					//	指定の文字が描画対象でなければ、豆腐を表示する
  					character = getMappedCharacter(NotMatchedSign.getCharacter());
  				}
  
  				stringWidth += character.getAdvance();
  			}
  		}
  
  		return stringWidth;
  	}
docs: Returns the total advance width for showing the specified String in the Font which is represented by this instance.<br>
  The advance is the distance from the leftmost point to the rightmost point on the string's baseline.<br>
  @param text the String to be measured
  @return the advance width of the specified String in the Font which is represented by this instance.