几秒前，几分钟前，几小时前，几天前，几月前，几年前的java实现

在代码开发的时候，特别是那种论坛啊什么的要返回“几秒前，几分钟前，几小时前，几天前，几月前，几年前”这样的时间格式，服务端那边只肯返回yyyy-MM-dd HH:mm:ss的格式，没办法，只能客户端加个转换了。

代码如下：

public class RelativeDateFormat {
private static final long ONE_MINUTE = 60000L;
private static final long ONE_HOUR = 3600000L;
private static final long ONE_DAY = 86400000L;
private static final long ONE_WEEK = 604800000L;

private static final String ONE_SECOND_AGO = "秒前";
private static final String ONE_MINUTE_AGO = "分钟前";
private static final String ONE_HOUR_AGO = "小时前";
private static final String ONE_DAY_AGO = "天前";
private static final String ONE_MONTH_AGO = "月前";
private static final String ONE_YEAR_AGO = "年前";

public static String format(Date date) {
long delta = new Date().getTime() - date.getTime();
if (delta < 1L * ONE_MINUTE) {
long seconds = toSeconds(delta);
return (seconds <= 0 ? 1 : seconds) + ONE_SECOND_AGO;
}
if (delta < 45L * ONE_MINUTE) {
long minutes = toMinutes(delta);
return (minutes <= 0 ? 1 : minutes) + ONE_MINUTE_AGO;
}
if (delta < 24L * ONE_HOUR) {
long hours = toHours(delta);
return (hours <= 0 ? 1 : hours) + ONE_HOUR_AGO;
}
if (delta < 48L * ONE_HOUR) {
return "昨天";
}
if (delta < 30L * ONE_DAY) {
long days = toDays(delta);
return (days <= 0 ? 1 : days) + ONE_DAY_AGO;
}
if (delta < 12L * 4L * ONE_WEEK) {
long months = toMonths(delta);
return (months <= 0 ? 1 : months) + ONE_MONTH_AGO;
} else {
long years = toYears(delta);
return (years <= 0 ? 1 : years) + ONE_YEAR_AGO;
}
}

private static long toSeconds(long date) {
return date / 1000L;
}

private static long toMinutes(long date) {
return toSeconds(date) / 60L;
}

private static long toHours(long date) {
return toMinutes(date) / 60L;
}

private static long toDays(long date) {
return toHours(date) / 24L;
}

private static long toMonths(long date) {
return toDays(date) / 30L;
}

private static long toYears(long date) {
return toMonths(date) / 365L;
}
}

调用的时候传入时间，今天是2016年1月20号

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date = null;
try {
date = format.parse("2015-11-11 18:35:35");
System.out.println(RelativeDateFormat.format(date));
} catch (ParseException e) {
e.printStackTrace();
}

看打印的log，算出来是没问题的。