java将输入的字符串时间提前一天，再以字符串形式输出

输入一个字符串时间后，程序将该时间提前一天后，再以字符串的形式输出

* 输入时间格式为：yyyy-MM-dd

     * */

    public String timeSub(String time){

        String year = time.substring(0,4);

        String monts = time.substring(5,7);

        String day = time.substring(8);

        int ye = Integer.parseInt(year);

        int mo = Integer.parseInt(monts);

        int da = Integer.parseInt(day);

        if(da != 1){

            da = da-1;

            if(da<10){

                time=year+"-"+monts+"-0"+da;

                return time;

            }else{

                time=year+"-"+monts+"-"+da;

                return time;

            }

        }else{

            da=30;

            if(mo != 1){

                mo = mo-1;

                if(mo < 10){

                    time = year+"-0"+mo+"-"+da;

                    return time;

                }else{

                    time=year+"-"+mo+"-"+da;

                    return time;

                }

            }else{

                mo=12;

                ye=ye-1;

                time=ye+"-"+mo+"-"+da;

                return time;

            }

        }

    }

}