如何将java.util.Date按dd/MM/yyyy格式返回？TimeAgo类时间格式修改

问题原因 #

你当前代码中超过三周的逻辑分支直接调用了Date.toString()方法，该方法会输出JDK默认的日期格式，不符合你需要的dd/MM/yyyy格式，只需修改该分支的日期格式化逻辑即可。

修正后代码 #

static class TimeAgo {
    private static final int SECOND_MILLIS = 1000;
    private static final int MINUTE_MILLIS = 60 * SECOND_MILLIS;
    private static final int HOUR_MILLIS = 60 * MINUTE_MILLIS;
    private static final int DAY_MILLIS = 24 * HOUR_MILLIS;
    private static final int WEEK_MILLIS = 7 * DAY_MILLIS ;
    // 定义目标日期格式，需要带时间可以改成 dd/MM/yyyy HH:mm
    private static final String DATE_PATTERN = "dd/MM/yyyy";

    public static String getTimeAgo(long time) {
        if (time < 1000000000000L) {
            time *= 1000;
        }

        long now = System.currentTimeMillis();
        if (time > now || time <= 0) {
            return null;
        }

        final long diff = now - time;
        if (diff < MINUTE_MILLIS) {
            return "刚刚";
        } else if (diff < 2 * MINUTE_MILLIS) {
            return "1分钟前";
        } else if (diff < 50 * MINUTE_MILLIS) {
            return diff / MINUTE_MILLIS + "分钟前";
        } else if (diff < 90 * MINUTE_MILLIS) {
            return "1小时前";
        } else if (diff < 24 * HOUR_MILLIS) {
            return diff / HOUR_MILLIS + "小时前";
        } else if (diff < 48 * HOUR_MILLIS) {
            return "昨天";
        } else if (diff < 72 * HOUR_MILLIS) {
            return "1天前";
        } else if (diff < 7 * DAY_MILLIS) {
            return diff / DAY_MILLIS + "天前";
        } else if (diff < 2 * WEEK_MILLIS) {
            return "1周前";
        } else if (diff < WEEK_MILLIS * 3) {
            return diff / WEEK_MILLIS + "周前";
        } else {
            java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(DATE_PATTERN);
            return sdf.format(new java.util.Date(time));
        }
    }
}

注意事项 #

如果你的项目使用Java 8及以上版本，更推荐用线程安全的DateTimeFormatter替换非线程安全的SimpleDateFormat，避免多线程调用出现格式错乱问题，修改方式如下：

1. 在类中全局定义格式化器（可复用）：

private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern(DATE_PATTERN);

2. 把else分支的代码替换为：

return Instant.ofEpochMilli(time).atZone(ZoneId.systemDefault()).format(DATE_FORMATTER);

内容的提问来源于stack exchange，提问作者Don Benito