将日期格式化成星期几

 public static string dayforweek(string ptime) throws throwable {  
	        simpledateformat format = new simpledateformat("yyyy-mm-dd");  
	        date tmpdate = format.parse(ptime);  
	        calendar cal = calendar.getinstance(); 
	        string[] weekdays = { "日", "一", "二", "三", "四", "五", "六" };
	        try {
	            cal.settime(tmpdate);
	        } catch (exception e) {
	            e.printstacktrace();
	        }
	        int w = cal.get(calendar.day_of_week) - 1; // 指示一个星期中的某天。
	        if (w < 0)
	            w = 0;
	        return weekdays[w];

	    }  

　　传入日期

public static void main(string[] args) throws throwable {

		 string a = dayforweek("2019-06-29 09:44:1");

}