code: public void randomlyDivideSave(double percentage, String fileName1, String fileName2) throws Exception {
  		ArrayList<String> rows = this.getDataRows();
  		Collections.shuffle(rows);
  		int portion = (int) (rows.size() * percentage);
  		for (int i = 0; i < portion; i++) {
  			this.hideRow(rows.get(i), true);
  		}
  		this.saveTXT(fileName2);
  		for (int i = 0; i < portion; i++) {
  			this.hideRow(rows.get(i), false);
  		}
  		for (int i = portion; i < rows.size(); i++) {
  			this.hideRow(rows.get(i), true);
  		}
  		this.saveTXT(fileName1);
  		for (int i = portion; i < rows.size(); i++) {
  			this.hideRow(rows.get(i), false);
  		}
  
  	}
docs: Split a worksheet randomly. Used for creating a discovery/validation data
  set The first file name will matched the percentage and the second file
  the remainder
  
  @param percentage
  @param fileName1
  @param fileName2
  @throws Exception