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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