Java星期的复选运算

基本实现原理：

代码实现如下：

/**
* Days of week code as a single int.
* 0x00: no day
* 0x01: Monday
* 0x02: Tuesday
* 0x04: Wednesday
* 0x08: Thursday
* 0x10: Friday
* 0x20: Saturday
* 0x40: Sunday
*/
public final class DaysOfWeek {

private static int[] DAY_MAP = new int[] {
Calendar.MONDAY,
Calendar.TUESDAY,
Calendar.WEDNESDAY,
Calendar.THURSDAY,
Calendar.FRIDAY,
Calendar.SATURDAY,
Calendar.SUNDAY,
};

// Bitmask of all repeating days
private int mDays;

DaysOfWeek(int days) {
mDays = days;
}

public String toString(boolean showNever) {
StringBuilder ret = new StringBuilder();

// no days
if (mDays == 0) {
return showNever ? "一律不" : "";
}

// every day
if (mDays == 0x7f) {
return "每天";
}

// count selected days
int dayCount = 0, days = mDays;
while (days > 0) {
if ((days & 1) == 1) dayCount++;
days >>= 1;
}

// short or long form?
DateFormatSymbols dfs = new DateFormatSymbols();
String[] dayList = (dayCount > 1) ?
dfs.getShortWeekdays() :
dfs.getWeekdays();

// selected days
for (int i = 0; i < 7; i++) {
if ((mDays & (1 << i)) != 0) {
ret.append(dayList[DAY_MAP[i]]);
dayCount -= 1;
if (dayCount > 0) ret.append(", ");
}
}
return ret.toString();
}

// 判断第几位是否被选中
private boolean isSet(int day) {
/*
* 如day为第三位
* (1 << day) 即为:00000100
* 00000100 与 mDays，只有当Days第三位为1时，才不等于0
*/
return ((mDays & (1 << day)) > 0);
}

public void set(int day, boolean set) {
if (set) {
mDays |= (1 << day);
} else {
mDays &= ~(1 << day);
}
}

public void set(DaysOfWeek dow) {
mDays = dow.mDays;
}

public int getCoded() {
return mDays;
}

// Returns days of week encoded in an array of booleans.
public boolean[] getBooleanArray() {
boolean[] ret = new boolean[7];
for (int i = 0; i < 7; i++) {
ret[i] = isSet(i);
}
return ret;
}

public boolean isRepeatSet() {
return mDays != 0;
}

/**
* returns number of days from today until next alarm
* @param c must be set to today
*/
public int getNextAlarm(Calendar c) {
if (mDays == 0) {
return -1;
}

int today = (c.get(Calendar.DAY_OF_WEEK) + 5) % 7;
int day = 0;
int dayCount = 0;
for (; dayCount < 7; dayCount++) {
// 今天加上将要发生的天数（1-7）
day = (today + dayCount) % 7;
if (isSet(day)) {
break;
}
}
return dayCount;
}
}

调用方法：

DaysOfWeek daysOfWeek = new DaysOfWeek(0x00);    // 初始化一个选中状态
daysOfWeek.set(0, true);    // 设置星期一选中
daysOfWeek.set(1, true);    // 设置星期二选中
daysOfWeek.set(0, false);   // 取消星期一的选中

// 获取选中的星期，第0位代表星期一
boolean[] weekBool = daysOfWeek.getBooleanArray();