这个目标日期计算器出了什么问题？

Question

我前段时间为我的项目写了这段代码，它应该计算用户可能实现其饮食目标的目标日期。但是在测试应用程序时，我发现无论目标是什么，目标日期总是比创建的日期晚一个月。

这是代码

    public String calcTD(SQLiteDatabase db){
    String date = null;
    myDataBase = db;
    Cursor c = myDataBase.rawQuery("SELECT * FROM USER", null);
    if (c!= null){
        if (c.moveToFirst()){
          String cdate = c.getString(c.getColumnIndex("CreatedDate"));              
          String type = c.getString(c.getColumnIndex("GoalType"));              
          if (type == "Maintain Weight")
                date = cdate;
          else{               
            int rate = c.getInt(c.getColumnIndex("Rate"));
            float gw = c.getFloat(c.getColumnIndex("GoalWeight"));
            float cw = getCW(db); //get current weight
            float w = 0; int days = 0;
            if (type == "Lose Weight")
                 w = cw - gw;
            else if (type == "Gain Weight")
                w = gw - cw;                
            switch (rate){
            case 0: // the rate 250g/week
                days = Math.round(w * 7 * 4); 
                break;
            case 1: //the rate 500g/week
                days = Math.round(w * 7 * 2); 
                break;
            case 2://the rate 750g/week
                days = Math.round(w * 7 * (4/3)) ;
                break;
            case 3:the rate 1kg/week
                days = Math.round(w * 7);
                break;
            }
            int y, m, d;
                            // the currentDate format (YYYYMMDD)
            y = Integer.parseInt(cdate.substring(0,4));
            m = Integer.parseInt(cdate.substring(4,6));
            d = Integer.parseInt(cdate.substring(6,8));             
            GregorianCalendar  i = new GregorianCalendar(y, m, d);
            i.add(Calendar.DAY_OF_MONTH, days);
            date = AllCmnMtd.getDate(i);    // this will convert the date to a string with format (yyyymmdd)            

            }               
        }
    }
    return date;    
}

很抱歉我是这么讨厌的人，但是我的项目答辩在两周内，我在测试应用程序的时候遇到了很多错误！！:(.

谢谢并致以最良好的问候

Answer 1

Java的Calendar类在月份中使用基于0的索引。例如。0是一月，11是十二月。

在放入Calendar对象之前，从m中减去1。