这个 try-catch 是如何工作的？

Question

我正在阅读的Java 代码是：

    private void validateCoordinatorJob() throws Exception {
        // check if startTime < endTime
        if (!coordJob.getStartTime().before(coordJob.getEndTime())) {
            throw new IllegalArgumentException("Coordinator Start Time must be earlier than End Time.");
        }

        try {
            // Check if a coord job with cron frequency will materialize actions
            int freq = Integer.parseInt(coordJob.getFrequency());

            // Check if the frequency is faster than 5 min if enabled
            if (ConfigurationService.getBoolean(CONF_CHECK_MAX_FREQUENCY)) {
                CoordinatorJob.Timeunit unit = coordJob.getTimeUnit();
                if (freq == 0 || (freq < 5 && unit == CoordinatorJob.Timeunit.MINUTE)) {
                    throw new IllegalArgumentException("Coordinator job with frequency [" + freq +
                            "] minutes is faster than allowed maximum of 5 minutes ("
                            + CONF_CHECK_MAX_FREQUENCY + " is set to true)");
                }
            }
        } catch (NumberFormatException e) {
            Date start = coordJob.getStartTime();
            Calendar cal = Calendar.getInstance();
            cal.setTime(start);
            cal.add(Calendar.MINUTE, -1);
            start = cal.getTime();

            Date nextTime = CoordCommandUtils.getNextValidActionTimeForCronFrequency(start, coordJob);
            if (nextTime == null) {
                throw new IllegalArgumentException("Invalid coordinator cron frequency: " + coordJob.getFrequency());
            }
            if (!nextTime.before(coordJob.getEndTime())) {
                throw new IllegalArgumentException("Coordinator job with frequency '" +
                        coordJob.getFrequency() + "' materializes no actions between start and end time.");
            }
        }
    }

我没有得到的是"Coordinator job with frequency [" + freq + "] minutes is faster than allowed maximum of 5 minutes ("+ CONF_CHECK_MAX_FREQUENCY + " is set to true)"日志是否可以打印。

据我所知，当if (freq == 0 || (freq < 5 && unit == CoordinatorJob.Timeunit.MINUTE))条件满足并且程序抛出 IllegalArgumentException 时。 抛出的异常将在catch (NumberFormatException e)处被捕获，并在该块中作为e处理。

但是那个e之后再也没有使用过。

所以我想知道是否可以按Coordinator job with frequency...日志。

对我来说，原始代码与将 catch 块放入if (freq == 0 || (freq < 5 && unit == CoordinatorJob.Timeunit.MINUTE))语句之间似乎没有区别，如下所示：

    private void validateCoordinatorJob() throws Exception {
        // check if startTime < endTime
        if (!coordJob.getStartTime().before(coordJob.getEndTime())) {
            throw new IllegalArgumentException("Coordinator Start Time must be earlier than End Time.");
        }

        // Check if a coord job with cron frequency will materialize actions
        int freq = Integer.parseInt(coordJob.getFrequency());

        // Check if the frequency is faster than 5 min if enabled
        if (ConfigurationService.getBoolean(CONF_CHECK_MAX_FREQUENCY)) {
            CoordinatorJob.Timeunit unit = coordJob.getTimeUnit();
            if (freq == 0 || (freq < 5 && unit == CoordinatorJob.Timeunit.MINUTE)) {
                Date start = coordJob.getStartTime();
                Calendar cal = Calendar.getInstance();
                cal.setTime(start);
                cal.add(Calendar.MINUTE, -1);
                start = cal.getTime();

                Date nextTime = CoordCommandUtils.getNextValidActionTimeForCronFrequency(start, coordJob);
                if (nextTime == null) {
                    throw new IllegalArgumentException("Invalid coordinator cron frequency: " + coordJob.getFrequency());
                }
                if (!nextTime.before(coordJob.getEndTime())) {
                    throw new IllegalArgumentException("Coordinator job with frequency '" +
                            coordJob.getFrequency() + "' materializes no actions between start and end time.");
                }
            }
        }
    }

Answer 1

catch 捕获NumberFormatException ，而不是IllegalArgumentException ，因此它不会捕获throw语句中抛出的异常。 NumberFormatException继承自IllegalArgumentException的事实并不重要。 catch子句在inheritance 树中捕获异常，而不是向上。 如果一个人可以接住所有的Tennisball ，而你向他们扔一个普通的Ball ，他们不会接住它，不是吗？

假设try子句中的其他方法没有抛出NumberFormatException ，那么catch子句旨在捕获Integer.parseInt抛出的NumberFormatException 。

所以我想知道是否可以按频率打印协调员工作......日志。

它可以由另一种方法打印出来，该方法在调用堆栈中进一步捕获异常。