计算下一个15分钟的开始时间

Calendar instance = Calendar.getInstance();

        int m = instance.get(Calendar.MINUTE);

        for (int i = 0; i < 4; i++) {
            if (m >= i * 15 && m < i * 15 + 15) {
                instance.add(Calendar.MINUTE, i * 15 + 15 - m);
                instance.set(Calendar.SECOND, 0);
                break;
            }
        }