java - Android - SimpleDateFormat IllegalArgumentException : Unknown pattern character 'u'

Question

日志猫:

FATAL EXCEPTION: main
java.lang.IllegalArgumentException: Unknown pattern character 'u'

这是我的代码:

long ticket = 1473808310826L;
SimpleDateFormat sdf = new SimpleDateFormat("u");
String test = sdf.format(ticket);

使用:JDK 8

u 用于 documentation SimpleDateFormat:

Day number of week (1 = Monday, ..., 7 = Sunday)

Answer 1

documentation SimpleDateFormat 具有误导性(截至09/16/2016，对于 future 的读者)。

Android 中没有 u 模式字符。

来自SimpleDateFormat的源代码:

static final String PATTERN_CHARS = "GyMdkHmsSEDFwWahKzZLc";

// ...

private void validatePatternCharacter(char format) {
    int index = PATTERN_CHARS.indexOf(format);
    if (index == -1) {
        throw new IllegalArgumentException("Unknown pattern character '"
            + format + "'");
    }
}

要获取当前星期几，您可以执行以下操作:

Calendar calendar = Calendar.getInstance();

// if you do not wish to use the current time, but a specific one
// calendar.setTimeInMillis(yourTimeInMillis);

switch (calendar.get(Calendar.DAY_OF_WEEK)) {
    case Calendar.MONDAY:
        // monday
        break;
    case Calendar.TUESDAY:
        // tuesday
        break;
    // ...
}