java修改系统时间

java修改系统时间/article/3794391.html

import java.io.IOException;
public class SetTime {
public static void main(String args[]){
String osName = System.getProperty("os.name");
String cmd = "";
try {
if (osName.matches("^(?i)Windows.*$")) {// Window 系统
// 格式 HH:mm:ss
cmd = "  cmd /c time 22:35:00";
Runtime.getRuntime().exec(cmd);
// 格式：yyyy-MM-dd
cmd = " cmd /c date 2009-03-26";
Runtime.getRuntime().exec(cmd);
} else {// Linux 系统
// 格式：yyyyMMdd
cmd = "  date -s 20090326";
Runtime.getRuntime().exec(cmd);
// 格式 HH:mm:ss
cmd = "  date -s 22:35:00";
Runtime.getRuntime().exec(cmd);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

---------------获取互联网时间-------------------
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
URL url=new URL("http://www.bjtime.cn");//取得资源对象
URLConnection uc=url.openConnection();//生成连接对象
uc.connect(); //发出连接
long ld=uc.getDate(); //取得网站日期时间
Date date=new Date(ld); //转换为标准时间对象
System.out.println(date);

}

------通过ntp 获取系统准确时间---------
本程序是java通过网络访问NTP时间服务器，而获得精准的时间。不是获得本地时间

Java代码import java.io.IOException;import java.io.InterruptedIOException;import java.net.ConnectException;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;import java.net.NoRouteToHostException;import java.net.UnknownHostException;public class TestNtp{public static void main(String[] args){int retry = 2;int port = 123;int timeout = 3000;// get the address and NTP address request//InetAddress ipv4Addr = null;try {ipv4Addr = InetAddress.getByName("203.117.180.36");//更多NTP时间服务器参考附注} catch (UnknownHostException e1) {e1.printStackTrace();}int serviceStatus = -1;DatagramSocket socket = null;long responseTime = -1;try {socket = new DatagramSocket();socket.setSoTimeout(timeout); // will force the// InterruptedIOExceptionfor (int attempts = 0; attempts <= retry && serviceStatus != 1; attempts++) {try {// Send NTP request//byte[] data = new NtpMessage().toByteArray();DatagramPacket outgoing = new DatagramPacket(data, data.length, ipv4Addr, port);long sentTime = System.currentTimeMillis();socket.send(outgoing);// Get NTP Response//// byte[] buffer = new byte[512];DatagramPacket incoming = new DatagramPacket(data, data.length);socket.receive(incoming);responseTime = System.currentTimeMillis() - sentTime;double destinationTimestamp = (System.currentTimeMillis() / 1000.0) + 2208988800.0;//这里要加2208988800，是因为获得到的时间是格林尼治时间，所以要变成东八区的时间，否则会与与北京时间有8小时的时差// Validate NTP Response// IOException thrown if packet does not decode as expected.NtpMessage msg = new NtpMessage(incoming.getData());double localClockOffset = ((msg.receiveTimestamp - msg.originateTimestamp) + (msg.transmitTimestamp - destinationTimestamp)) / 2;System.out.println("poll: valid NTP request received the local clock offset is " + localClockOffset + ", responseTime= " + responseTime + "ms");System.out.println("poll: NTP message : " + msg.toString());serviceStatus = 1;} catch (InterruptedIOException ex) {// Ignore, no response received.}}} catch (NoRouteToHostException e) {System.out.println("No route to host exception for address: " + ipv4Addr);} catch (ConnectException e) {// Connection refused. Continue to retry.e.fillInStackTrace();System.out.println("Connection exception for address: " + ipv4Addr);} catch (IOException ex) {ex.fillInStackTrace();System.out.println("IOException while polling address: " + ipv4Addr);} finally {if (socket != null)socket.close();}// Store response time if available//if (serviceStatus == 1) {System.out.println("responsetime=="+responseTime);}}}

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.ConnectException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.NoRouteToHostException;
import java.net.UnknownHostException;

public class TestNtp{

public static void main(String[] args){
int retry = 2;
int port = 123;
int timeout = 3000;

// get the address and NTP address request
//
InetAddress ipv4Addr = null;
try {
ipv4Addr = InetAddress.getByName("203.117.180.36");//更多NTP时间服务器参考附注
} catch (UnknownHostException e1) {
e1.printStackTrace();
}

int serviceStatus = -1;
DatagramSocket socket = null;
long responseTime = -1;
try {
socket = new DatagramSocket();
socket.setSoTimeout(timeout); // will force the
// InterruptedIOException

for (int attempts = 0; attempts <= retry && serviceStatus != 1; attempts++) {
try {
// Send NTP request
//
byte[] data = new NtpMessage().toByteArray();
DatagramPacket outgoing = new DatagramPacket(data, data.length, ipv4Addr, port);
long sentTime = System.currentTimeMillis();
socket.send(outgoing);

// Get NTP Response
//
// byte[] buffer = new byte[512];
DatagramPacket incoming = new DatagramPacket(data, data.length);
socket.receive(incoming);
responseTime = System.currentTimeMillis() - sentTime;
double destinationTimestamp = (System.currentTimeMillis() / 1000.0) + 2208988800.0;
//这里要加2208988800，是因为获得到的时间是格林尼治时间，所以要变成东八区的时间，否则会与与北京时间有8小时的时差

// Validate NTP Response
// IOException thrown if packet does not decode as expected.
NtpMessage msg = new NtpMessage(incoming.getData());
double localClockOffset = ((msg.receiveTimestamp - msg.originateTimestamp) + (msg.transmitTimestamp - destinationTimestamp)) / 2;

System.out.println("poll: valid NTP request received the local clock offset is " + localClockOffset + ", responseTime= " + responseTime + "ms");
System.out.println("poll: NTP message : " + msg.toString());
serviceStatus = 1;
} catch (InterruptedIOException ex) {
// Ignore, no response received.
}
}
} catch (NoRouteToHostException e) {
System.out.println("No route to host exception for address: " + ipv4Addr);
} catch (ConnectException e) {
// Connection refused. Continue to retry.
e.fillInStackTrace();
System.out.println("Connection exception for address: " + ipv4Addr);
} catch (IOException ex) {
ex.fillInStackTrace();
System.out.println("IOException while polling address: " + ipv4Addr);
} finally {
if (socket != null)
socket.close();
}

// Store response time if available
//
if (serviceStatus == 1) {
System.out.println("responsetime=="+responseTime);
}

}
}

Java代码import java.text.DecimalFormat;import java.text.SimpleDateFormat;import java.util.Date;public class NtpMessage {/** *//*** This is a two-bit code warning of an impending leap second to be* inserted/deleted in the last minute of the current day. It''s values may* be as follows:** Value Meaning ----- ------- 0 no warning 1 last minute has 61 seconds 2* last minute has 59 seconds) 3 alarm condition (clock not synchronized)*/public byte leapIndicator = 0;/** *//*** This value indicates the NTP/SNTP version number. The version number is 3* for Version 3 (IPv4 only) and 4 for Version 4 (IPv4, IPv6 and OSI). If* necessary to distinguish between IPv4, IPv6 and OSI, the encapsulating* context must be inspected.*/public byte version = 3;/** *//*** This value indicates the mode, with values defined as follows:** Mode Meaning ---- ------- 0 reserved 1 symmetric active 2 symmetric* passive 3 client 4 server 5 broadcast 6 reserved for NTP control message* 7 reserved for private use** In unicast and anycast modes, the client sets this field to 3 (client) in* the request and the server sets it to 4 (server) in the reply. In* multicast mode, the server sets this field to 5 (broadcast).*/public byte mode = 0;/** *//*** This value indicates the stratum level of the local clock, with values* defined as follows:** Stratum Meaning ---------------------------------------------- 0* unspecified or unavailable 1 primary reference (e.g., radio clock) 2-15* secondary reference (via NTP or SNTP) 16-255 reserved*/public short stratum = 0;/** *//*** This value indicates the maximum interval between successive messages, in* seconds to the nearest power of two. The values that can appear in this* field presently range from 4 (16 s) to 14 (16284 s); however, most* applications use only the sub-range 6 (64 s) to 10 (1024 s).*/public byte pollInterval = 0;/** *//*** This value indicates the precision of the local clock, in seconds to the* nearest power of two. The values that normally appear in this field* range from -6 for mains-frequency clocks to -20 for microsecond clocks* found in some workstations.*/public byte precision = 0;/** *//*** This value indicates the total roundtrip delay to the primary reference* source, in seconds. Note that this variable can take on both positive and* negative values, depending on the relative time and frequency offsets.* The values that normally appear in this field range from negative values* of a few milliseconds to positive values of several hundred milliseconds.*/public double rootDelay = 0;/** *//*** This value indicates the nominal error relative to the primary reference* source, in seconds. The values that normally appear in this field range* from 0 to several hundred milliseconds.*/public double rootDispersion = 0;/** *//*** This is a 4-byte array identifying the particular reference source. In* the case of NTP Version 3 or Version 4 stratum-0 (unspecified) or* stratum-1 (primary) servers, this is a four-character ASCII string, left* justified and zero padded to 32 bits. In NTP Version 3 secondary servers,* this is the 32-bit IPv4 address of the reference source. In NTP Version 4* secondary servers, this is the low order 32 bits of the latest transmit* timestamp of the reference source. NTP primary (stratum 1) servers should* set this field to a code identifying the external reference source* according to the following list. If the external reference is one of* those listed, the associated code should be used. Codes for sources not* listed can be contrived as appropriate.** Code External Reference Source ---- ------------------------- LOCL* uncalibrated local clock used as a primary reference for a subnet without* external means of synchronization PPS atomic clock or other* pulse-per-second source individually calibrated to national standards* ACTS NIST dialup modem service USNO USNO modem service PTB PTB (Germany)* modem service TDF Allouis (France) Radio 164 kHz DCF Mainflingen* (Germany) Radio 77.5 kHz MSF Rugby (UK) Radio 60 kHz WWV Ft. Collins (US)* Radio 2.5, 5, 10, 15, 20 MHz WWVB Boulder (US) Radio 60 kHz WWVH Kaui* Hawaii (US) Radio 2.5, 5, 10, 15 MHz CHU Ottawa (Canada) Radio 3330,* 7335, 14670 kHz LORC LORAN-C radionavigation system OMEG OMEGA* radionavigation system GPS Global Positioning Service GOES Geostationary* Orbit Environment Satellite*/public byte[] referenceIdentifier = { 0, 0, 0, 0 };/** *//*** This is the time at which the local clock was last set or corrected, in* seconds since 00:00 1-Jan-1900.*/public double referenceTimestamp = 0;/** *//*** This is the time at which the request departed the client for the server,* in seconds since 00:00 1-Jan-1900.*/public double originateTimestamp = 0;/** *//*** This is the time at which the request arrived at the server, in seconds* since 00:00 1-Jan-1900.*/public double receiveTimestamp = 0;/** *//*** This is the time at which the reply departed the server for the client,* in seconds since 00:00 1-Jan-1900.*/public double transmitTimestamp = 0;/** *//*** Constructs a new NtpMessage from an array of bytes.*/public NtpMessage(byte[] array) {// See the packet format diagram in RFC 2030 for detailsleapIndicator = (byte) ((array[0] >> 6) & 0x3);version = (byte) ((array[0] >> 3) & 0x7);mode = (byte) (array[0] & 0x7);stratum = unsignedByteToShort(array[1]);pollInterval = array[2];precision = array[3];rootDelay = (array[4] * 256.0) + unsignedByteToShort(array[5]) + (unsignedByteToShort(array[6]) / 256.0) + (unsignedByteToShort(array[7]) / 65536.0);rootDispersion = (unsignedByteToShort(array[8]) * 256.0) + unsignedByteToShort(array[9]) + (unsignedByteToShort(array[10]) / 256.0) + (unsignedByteToShort(array[11]) / 65536.0);referenceIdentifier[0] = array[12];referenceIdentifier[1] = array[13];referenceIdentifier[2] = array[14];referenceIdentifier[3] = array[15];referenceTimestamp = decodeTimestamp(array, 16);originateTimestamp = decodeTimestamp(array, 24);receiveTimestamp = decodeTimestamp(array, 32);transmitTimestamp = decodeTimestamp(array, 40);}/** *//*** Constructs a new NtpMessage*/public NtpMessage(byte leapIndicator, byte version, byte mode, short stratum, byte pollInterval, byte precision, double rootDelay, double rootDispersion, byte[] referenceIdentifier, double referenceTimestamp, double originateTimestamp, double receiveTimestamp, double transmitTimestamp) {// ToDo: Validity checkingthis.leapIndicator = leapIndicator;this.version = version;this.mode = mode;this.stratum = stratum;this.pollInterval = pollInterval;this.precision = precision;this.rootDelay = rootDelay;this.rootDispersion = rootDispersion;this.referenceIdentifier = referenceIdentifier;this.referenceTimestamp = referenceTimestamp;this.originateTimestamp = originateTimestamp;this.receiveTimestamp = receiveTimestamp;this.transmitTimestamp = transmitTimestamp;}/** *//*** Constructs a new NtpMessage in client -> server mode, and sets the* transmit timestamp to the current time.*/public NtpMessage() {// Note that all the other member variables are already set with// appropriate default values.this.mode = 3;this.transmitTimestamp = (System.currentTimeMillis() / 1000.0) + 2208988800.0;}/** *//*** This method constructs the data bytes of a raw NTP packet.*/public byte[] toByteArray() {// All bytes are automatically set to 0byte[] p = new byte[48];p[0] = (byte) (leapIndicator << 6 | version << 3 | mode);p[1] = (byte) stratum;p[2] = (byte) pollInterval;p[3] = (byte) precision;// root delay is a signed 16.16-bit FP, in Java an int is 32-bitsint l = (int) (rootDelay * 65536.0);p[4] = (byte) ((l >> 24) & 0xFF);p[5] = (byte) ((l >> 16) & 0xFF);p[6] = (byte) ((l >> 8) & 0xFF);p[7] = (byte) (l & 0xFF);// root dispersion is an unsigned 16.16-bit FP, in Java there are no// unsigned primitive types, so we use a long which is 64-bitslong ul = (long) (rootDispersion * 65536.0);p[8] = (byte) ((ul >> 24) & 0xFF);p[9] = (byte) ((ul >> 16) & 0xFF);p[10] = (byte) ((ul >> 8) & 0xFF);p[11] = (byte) (ul & 0xFF);p[12] = referenceIdentifier[0];p[13] = referenceIdentifier[1];p[14] = referenceIdentifier[2];p[15] = referenceIdentifier[3];encodeTimestamp(p, 16, referenceTimestamp);encodeTimestamp(p, 24, originateTimestamp);encodeTimestamp(p, 32, receiveTimestamp);encodeTimestamp(p, 40, transmitTimestamp);return p;}/** *//*** Returns a string representation of a NtpMessage*/public String toString() {String precisionStr = new DecimalFormat("0.#E0").format(Math.pow(2, precision));return "Leap indicator: " + leapIndicator + " " + "Version: " + version + " " + "Mode: " + mode + " " + "Stratum: " + stratum + " " + "Poll: " + pollInterval + " " + "Precision: " + precision + " (" + precisionStr + " seconds) " + "Root delay: " + new DecimalFormat("0.00").format(rootDelay * 1000) + " ms " + "Root dispersion: " + new DecimalFormat("0.00").format(rootDispersion * 1000) + " ms " + "Reference identifier: " + referenceIdentifierToString(referenceIdentifier, stratum, version) + " " + "Reference timestamp: " + timestampToString(referenceTimestamp) + " " + "Originate timestamp: " + timestampToString(originateTimestamp) + " " + "Receive timestamp: " + timestampToString(receiveTimestamp) + " " + "Transmit timestamp: " + timestampToString(transmitTimestamp);}/** *//*** Converts an unsigned byte to a short. By default, Java assumes that a* byte is signed.*/public static short unsignedByteToShort(byte b) {if ((b & 0x80) == 0x80)return (short) (128 + (b & 0x7f));elsereturn (short) b;}/** *//*** Will read 8 bytes of a message beginning at <code>pointer</code> and* return it as a double, according to the NTP 64-bit timestamp format.*/public static double decodeTimestamp(byte[] array, int pointer) {double r = 0.0;for (int i = 0; i < 8; i++) {r += unsignedByteToShort(array[pointer + i]) * Math.pow(2, (3 - i) * 8);}return r;}/** *//*** Encodes a timestamp in the specified position in the message*/public static void encodeTimestamp(byte[] array, int pointer, double timestamp) {// Converts a double into a 64-bit fixed pointfor (int i = 0; i < 8; i++) {// 2^24, 2^16, 2^8, .. 2^-32double base = Math.pow(2, (3 - i) * 8);// Capture byte valuearray[pointer + i] = (byte) (timestamp / base);// Subtract captured value from remaining totaltimestamp = timestamp - (double) (unsignedByteToShort(array[pointer + i]) * base);}// From RFC 2030: It is advisable to fill the non-significant// low order bits of the timestamp with a random, unbiased// bitstring, both to avoid systematic roundoff errors and as// a means of loop detection and replay detection.array[7] = (byte) (Math.random() * 255.0);}/** *//*** Returns a timestamp (number of seconds since 00:00 1-Jan-1900) as a* formatted date/time string.*/public static String timestampToString(double timestamp) {if (timestamp == 0)return "0";// timestamp is relative to 1900, utc is used by Java and is relative// to 1970double utc = timestamp - (2208988800.0);// millisecondslong ms = (long) (utc * 1000.0);// date/timeString date = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss").format(new Date(ms));// fractiondouble fraction = timestamp - ((long) timestamp);String fractionSting = new DecimalFormat(".000000").format(fraction);return date + fractionSting;}/** *//*** Returns a string representation of a reference identifier according to* the rules set out in RFC 2030.*/public static String referenceIdentifierToString(byte[] ref, short stratum, byte version) {// From the RFC 2030:// In the case of NTP Version 3 or Version 4 stratum-0 (unspecified)// or stratum-1 (primary) servers, this is a four-character ASCII// string, left justified and zero padded to 32 bits.if (stratum == 0 || stratum == 1) {return new String(ref);}// In NTP Version 3 secondary servers, this is the 32-bit IPv4// address of the reference source.else if (version == 3) {return unsignedByteToShort(ref[0]) + "." + unsignedByteToShort(ref[1]) + "." + unsignedByteToShort(ref[2]) + "." + unsignedByteToShort(ref[3]);}// In NTP Version 4 secondary servers, this is the low order 32 bits// of the latest transmit timestamp of the reference source.else if (version == 4) {return "" + ((unsignedByteToShort(ref[0]) / 256.0) + (unsignedByteToShort(ref[1]) / 65536.0) + (unsignedByteToShort(ref[2]) / 16777216.0) + (unsignedByteToShort(ref[3]) / 4294967296.0));}return "";}}