求帮写一个java小程序

参考代码如下：

 import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class DateCalendar {
    public static void main(String[] args) {
        printLatestMonth("src/date.txt");
    }

    public static void printLatestMonth(String filePath){
        String fileContent = readFromFile(filePath,null);
        if(fileContent==null||fileContent.length()<8){
            System.out.println("日期格式不正确，请保证日期格式为yyyyMMdd");
            return;
        }

        DateFormat format = new SimpleDateFormat("yyyyMMdd");
        Calendar calendar = Calendar.getInstance();
        try {
            Date currentDate  = format.parse(fileContent);
            calendar.setTime(currentDate);
            System.out.println("crurent date is:"+currentDate);
            for(int i = 0;i<30;i++){
                calendar.add(Calendar.DATE, 1);
                System.out.println(calendar.getTime());
            }
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static String readFromFile(String fileName,String charSet){
        if (fileName == null || "".equals(fileName)) {
            System.out.println("文件名称为空...");
            return "";
        }

        // 设置字符编码
        if(charSet==null||charSet.length()==0){
            charSet = "UTF-8";
        }

        File file = new File(fileName);
        FileInputStream fin = null;
        StringBuffer buffer = new StringBuffer();
        try {
            fin = new FileInputStream(file);
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    fin, charSet));
            String content = reader.readLine();
            while (content != null) {
                buffer.append(content);
                // 循环读取下一行，没有这行代码就是死循环的啦。。。
                content = reader.readLine();
            }
            reader.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fin != null) {
                try {
                    fin.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        return buffer.toString();
    }
}

src目录下文件格式:20160310