蜗牛—Java基础之学习(三)

最近在学习Date、Calendar及SimpleDateFormat出了一点情况，有点乱。嗯，真的有点乱了

一、Calendar与Date转化

1、

Calendar calendar = Calendar.getInstance();
Date date = calendar.getTime();
System.out.println(date);

2、

Date date2 = new Date();
calendar.setTime(date2);
System.out.println(calendar.get(Calendar.YEAR));

二、格式化输出时间

Date date3 = new Date();
SimpleDateFormat df = new SimpleDateFormat("yy-MM-dd hh:mm:ss");
System.out.println(df.format(date3));

三、计算某一天是一年的第几星期(月份是从0开始的)

Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, 2014);
calendar.set(Calendar.MONTH, 2);
calendar.set(Calendar.DAY_OF_MONTH, 11);
System.out.println(calendar.get(Calendar.WEEK_OF_YEAR));

四、计算一年中的第几星期的星期几      是几号

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, 2014);
calendar.set(Calendar.WEEK_OF_YEAR, 11);
calendar.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
System.out.println(simpleDateFormat.format(calendar.getTime()));

五、Date与String之间的转换

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = null;
String string = "2014-03-11";
try {
date = simpleDateFormat.parse(string);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(simpleDateFormat.format(date));