有关日期的简单处理

/**
* 获得当月的最后一天 */
public String getLastDay(){
Calendar c = Calendar.getInstance();
c.set(Calendar.DATE, 1);
c.roll(Calendar.DATE, -1);
int lastDay = c.get(Calendar.DATE);
return Integer.toString(lastDay);
}


/**
* 获得当月的下一个月日期
*/
public String getNextMonth(){

                  Calendar rightNow = Calendar.getInstance();
String year = Integer.toString(rightNow.get(Calendar.YEAR));
int month = rightNow.get(Calendar.MONTH)+1;
int day = rightNow.get(Calendar.DATE);

String monthString = null;
String dayString = null;
if (month<10) {
monthString = "0"+month;
}else {
monthString= Integer.toString(month);
}

if (day<10) {
dayString = "0"+day;
}else {
dayString = Integer.toString(day);
}

rightNowString = year+"-" +monthString+"-" +dayString;
}


/**
* 获得当前日期的前后几天日期 */

private String getDate(int diff){
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
java.util.Date date = new java.util.Date();
Calendar calendar = Calendar.getInstance(); 
calendar.setTime(date);  
calendar.add(Calendar.DATE,diff);      
Date newDate  = calendar.getTime();
return sdf.format(newDate);
}