Date today = new Date();   //当前时间
Calendar calendar = Calendar.getInstance(); //得到日历
calendar.setTime(today);//把当前时间赋给日历
calendar.add(Calendar.DAY_OF_MONTH, -1);  //设置为前一天
Date yesterday = calendar.getTime();   //得到前一天的时间
calendar.setTime(today);
calendar.add(Calendar.DAY_OF_MONTH, 1);  //设置为后一天
Date tomorrow = calendar.getTime();   //得到后一天的时间SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); //设置时间格式
System.out.println("今天是：" + sdf.format(today));
System.out.println("昨天是：" + sdf.format(yesterday));
System.out.println("明天是：" + sdf.format(tomorrow));calendar.setTime(today);
calendar.add(Calendar.DAY_OF_MONTH, -7);
Date baforeWeek = calendar.getTime();
calendar.setTime(today);
calendar.add(Calendar.DAY_OF_MONTH, 7);
Date afterWeek = calendar.getTime();
System.out.println("前一周是：" + sdf.format(baforeWeek));
System.out.println("后一周是：" + sdf.format(afterWeek));calendar.setTime(today);
calendar.add(Calendar.MONTH, -1);
Date beforeMonth = calendar.getTime();
calendar.setTime(today);
calendar.add(Calendar.MONTH, 1);
Date afterMonth = calendar.getTime();
System.out.println("前一月是：" + sdf.format(beforeMonth));
System.out.println("后一月是：" + sdf.format(afterMonth));calendar.setTime(today);
calendar.add(Calendar.YEAR, -1);
Date beforeYear = calendar.getTime();
calendar.setTime(today);
calendar.add(Calendar.YEAR, 1);
Date afterYear = calendar.getTime();
System.out.println("前一年是：" + sdf.format(beforeYear));
System.out.println("后一年是：" + sdf.format(afterYear));