code: public void setPattern(String pattern) throws IllegalArgumentException{
  		if (pattern == null) {
  			throw new IllegalArgumentException("The pattern must not be null.");
  		}
  
  		this.pattern = pattern;
  		parsePattern(this.pattern);
  	}
docs: Set the pattern that is when formatting.
  
  @param pattern
  the pattern to set
  @throws IllegalArgumentException
  if the pattern is null.