public class TxtWrite {

    public static void main(String args[]){

        contentToTxt("D:\\xyky.txt","3");

    }

    public static void contentToTxt(String filePath, String content) {

        try{

            BufferedWriter writer = new BufferedWriter(new FileWriter(new File(filePath),true));

            writer.write("\n"+content);

            writer.close();

        }catch(Exception e){

            e.printStackTrace();

        }

    }

}