java判断当前是星期几&日期格式化&获取前一天日期

1.判断当前日期是星期几：

Date date = new Date();

Calendar cal = Calendar.getInstance();

cal.setTime(date);

int week = cal.get(Calendar.DAY_OF_WEEK) - 1;//0是星期天，6是星期六

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2.格式化日期格式：

Date date = new Date();

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");

String today = format.format(date);

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3.跳转到指定日期：

Date date = new Date();

Calendar cal = Calendar.getInstance();

cal.setTime(date);

cal.add(Calendar.DAY_OF_YEAR, -1);

date = cal.getTime();

yesterday = format.format(date);