Java-如何判斷日期字符串是否為周末

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 * @description: 判斷日期字符串是否為周末
 */
public class IsWeekend {
    public boolean isWeekend(String dateStr) {
        boolean isWeekend = false;
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            Date date = sdf.parse(dateStr);
            Calendar cal = Calendar.getInstance();
            cal.setTime(date);
            isWeekend = cal.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY || cal.get(Calendar.DAY_OF_WEEK) == Calendar.SUNDAY;
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return isWeekend;
    }

　　

/**
     * 根據日期獲取當前是星期幾
     */
    public static void main(String[] args) throws ParseException {
        String dates = "2020-12-1";
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");
        Date d =f.parse(dates);
        cal.setTime(d);
        //因為數組下標從0開始，而返回的是數組的內容，是數組{1,2,3,4,5,6,7}中用1~7來表示，所以要減1
        int w=cal.get(Calendar.DAY_OF_WEEK)-1;
        if(w==0) {
            w=7;
        };
        System.out.println("星期"+w);
        //輸出：星期2
    }

}