http://hi.baidu.com/captives/item/25c8b80170a9b0ccf45ba6f8
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package dtm.tools;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* SyncTime 获取原子钟的时间，并设置为系统时间
* @author Administrator
*/
public class SyncTime {
private static int sleepMinutes = 0;
private static final long EPOCH_OFFSET_MILLIS;
private static final String[] hostName = {"time-a.nist.gov", "time-nw.nist.gov", "time.nist.gov"};
static {
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
// Java使用的参照标准是1970年，而时间服务器返回的秒是相当1900年的，算一下偏移
calendar.set(1900, Calendar.JANUARY, 1, 0, 0, 0);
EPOCH_OFFSET_MILLIS = Math.abs(calendar.getTime().getTime());
}
public static void main(String[] args) {
GetWebTime();
}
private static Date getNetDate(String hostName) {
Date date = null;
long result = 0;
try {
Socket socket = new Socket(hostName, 37);
BufferedInputStream bis = new BufferedInputStream(socket.getInputStream(),
socket.getReceiveBufferSize());
int b1 = bis.read();
int b2 = bis.read();
int b3 = bis.read();
int b4 = bis.read();
if ((b1 | b2 | b3 | b3) < 0) {
return null;
}
result = (((long) b1) << 24) + (b2 << 16) + (b3 << 8) + b4;
date = new Date(result * 1000 - EPOCH_OFFSET_MILLIS);
socket.close();
} catch (UnknownHostException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
}
return date;
}
/**
* 通过ping命令判断是否离线
* @return
*/
public static boolean offLine() {
Runtime run = Runtime.getRuntime();
try {
Process process = run.exec("ping www.hao123.com");
InputStream s = process.getInputStream();
BufferedReader bis = new BufferedReader(new InputStreamReader(s));
String str = bis.readLine();
while (str != null) {
if (str.startsWith("Reply from")) {
return false;
}
str = bis.readLine();
}
process.waitFor();
} catch (IOException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
} catch (InterruptedException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
}
return true;
}
/**
* 通过调用本地命令date和time修改计算机时间
* @param date
*/
private static void setComputeDate(Date date) {
Calendar c = Calendar.getInstance(TimeZone.getTimeZone("GMT+8"));
c.setTime(date);
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH) + 1;
int day = c.get(Calendar.DAY_OF_MONTH);
int hour = c.get(Calendar.HOUR_OF_DAY);
int minute = c.get(Calendar.MINUTE);
int second = c.get(Calendar.SECOND);
c.setTime(new Date());
int year_c = c.get(Calendar.YEAR);
int month_c = c.get(Calendar.MONTH) + 1;
int day_c = c.get(Calendar.DAY_OF_MONTH);
int hour_c = c.get(Calendar.HOUR_OF_DAY);
int minute_c = c.get(Calendar.MINUTE);
String ymd = year + "-" + month + "-" + day;
String time = hour + ":" + minute + ":" + second;
try {
// 日期不一致就修改一下日期
if (year != year_c || month != month_c || day != day_c) {
String cmd = "cmd /c date " + ymd;
Process process = Runtime.getRuntime().exec(cmd);
process.waitFor();
}
// 时间不一致就修改一下时间
if (hour != hour_c || minute != minute_c) {
String cmd = "cmd /c time " + time;
Process process = Runtime.getRuntime().exec(cmd);
process.waitFor();
}
} catch (IOException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
} catch (InterruptedException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
}
}
public static void GetWebTime()
{
// 检测电脑是否在线
while (offLine() && sleepMinutes < 30) {
try {
Thread.sleep(120000);
sleepMinutes += 2;
} catch (InterruptedException ex) {
Logger.getLogger(SyncTime.class.getName()).log(Level.SEVERE, null, ex);
}
}
// 30分钟还没有联线，表示就不上网了，退出吧
if (sleepMinutes >= 30)
{
System.exit(0);
}
// 从网络上获取时间
Date date = null;
for (int i = 0; i < hostName.length; i++) {
date = getNetDate(hostName[i]);
if (date != null) {
break;
}
}
// 修改本机时间
if (date != null) {
System.out.println("原子钟时间："+date);
setComputeDate(date);
}
}
}
java 获取服务器时间同步本地计算机时间,布布扣,bubuko.com