java获取这周的开始时间

public static void main(String[] args) {

		Calendar c=Calendar.getInstance();
		SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
		//今天
		String today=df.format("今天时间："+c.getTime());
		System.out.println(today);
		//今天是周几
		int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);
               //
		dayOfWeek-=2;
		//今天-1天（昨天）
		c.add(Calendar.DAY_OF_MONTH, -dayOfWeek);

		String yesterday=df.format(c.getTime());

		System.out.println("周一时间   "+yesterday);

		System.out.println("今天周几   "+dayOfWeek);
	}