JAVA判断某天是周几

java判断周六周日，周一到周五

!> 这里利用到了Calendar类

DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String Date = "2020-08-03"; //定义初始是周一
Date testdate = sdf.parse(Date);
Calendar cal = Calendar.getInstance();
cal.setTime(testdate);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.MONDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周一=========");
}
//日期加一天
cal.add(Calendar.DATE, 1);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.TUESDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周二=========");
}
cal.add(Calendar.DATE, 1);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.WEDNESDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周三=========");
}
cal.add(Calendar.DATE, 1);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.THURSDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周四=========");
}
cal.add(Calendar.DATE, 1);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.FRIDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周五=========");
}
cal.add(Calendar.DATE, 1);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周六=========");
}
cal.add(Calendar.DATE, 1);
if(cal.get(Calendar.DAY_OF_WEEK) == Calendar.SUNDAY)
{
    System.out.println(sdf.format(cal.getTime()) + "=========" + "是周日=========");
}

结果打印：

2020-08-03=========是周一=========
2020-08-04=========是周二=========
2020-08-05=========是周三=========
2020-08-06=========是周四=========
2020-08-07=========是周五=========
2020-08-08=========是周六=========
2020-08-09=========是周日=========

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