java日期增加和减少

Calendar cal = Calendar.getInstance();
cal.add(Calendar.MONTH,1);//月份+1
Date  time = cal.getTime()

cal.add(Calendar.YEAR,1);//年份+1
Date  time = cal.getTime()

cal.add(Calendar.DATE,1);//天+1
Date  time = cal.getTime()

//上个月
cal.set(Calendar.DAY_OF_MONTH,-1);//当前月的第几天
Date  time = cal.getTime()

//其他以此类推