code: public String formatErrors() {
  
  		if (errors.size() > 0) {
  
  			StringBuilder results = new StringBuilder();
  
  			for (Throwable t : errors) {
  				results.append(t.getMessage());
  				results.append("\n");
  				if (t instanceof NullPointerException
  						|| t instanceof CompilerError) {
  
  					results.append(formatStackTrace(t));
  
  				} else if (t instanceof SystemException) {
  
  					results.append(formatStackTrace(t));
  
  					Throwable cause = t.getCause();
  					if (cause != null) {
  						results.append("\nCause:\n");
  						results.append(cause.getMessage());
  						results.append("\n");
  					}
  					results.append(formatStackTrace(t));
  				}
  			}
  			return results.toString();
  		} else {
  			return null;
  		}
  	}
docs: Format the exceptions thrown during the compilation process. A null value
  will be returned if no exceptions were thrown.
  
  @return String containing exceptions thrown during execution or null if
  none were thrown