com.pamirs.pradar.FastDateFormat Maven / Gradle / Ivy
package com.pamirs.pradar;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
/**
* 固定输出的时间戳格式：yyyy-MM-dd HH:mm:ss.SSS
* 与 SimpleDateFormat 相比，差别是：
*
* - 针对同一秒频繁输出的时间戳做了缓存
*
- 不管在什么时区，输出的时间都校正到中国的东八区
*
* 这个类非线程安全，使用时需要做 SimpleDateFormat 类似的线程保护
*/
class FastDateFormat {
private static final long TIMEZONE_GMT_ADD_8_OFFSET = 28800000;
/**
* 当前时区的时间（含夏令时）与中国东八区 "GMT+8" 的偏移量
*/
private static final long CURRENT_TIMEZONE_OFFSET = TimeZone.getDefault().getOffset(0)
+ TimeZone.getDefault().getDSTSavings() - TIMEZONE_GMT_ADD_8_OFFSET;
private final SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
private char[] buffer = new char[23];
private long lastSecond = -1;
public String format(long timestamp) {
formatToBuffer(timestamp);
return new String(buffer, 0, 23);
}
public String format(Date date) {
return format(date.getTime());
}
public void formatAndAppendTo(long timestamp, StringBuilder appender) {
formatToBuffer(timestamp);
appender.append(buffer, 0, 23);
}
private void formatToBuffer(long timestamp) {
final long ts = timestamp - CURRENT_TIMEZONE_OFFSET;
long second = ts / 1000;
if (second == lastSecond) {
int ms = (int) (ts % 1000);
buffer[22] = (char) (ms % 10 + '0');
ms /= 10;
buffer[21] = (char) (ms % 10 + '0');
buffer[20] = (char) (ms / 10 + '0');
} else {
String result = fmt.format(new Date(ts));
result.getChars(0, result.length(), buffer, 0);
}
}
String formatWithoutMs(long timestamp) {
final long ts = timestamp - CURRENT_TIMEZONE_OFFSET;
long second = ts / 1000;
if (second != lastSecond) {
String result = fmt.format(new Date(ts));
result.getChars(0, result.length(), buffer, 0);
}
return new String(buffer, 0, 19);
}
}