//方案：使用java.net.ServerSocket
//問(wèn)題：打開(kāi)服務(wù)端口可能會(huì)受到防火墻的影響；可能和別的端口沖突。
import java.io.*;
import java.net.*;
public class OneInstance_2
{
    private static ServerSocket listenerSocket;
    public static void main(String[] args)
    {
        try
        {
            listenerSocket = new ServerSocket(2004);
            //At this point, no other socket may listen on port 2004.
        }
        catch(java.net.BindException e)
        {
            System.err.println("A previous instance is already running....");
            System.exit(1);
        }
        catch(final IOException e)     // an unexpected exception occurred
        {
            System.exit(1);
        }
        // Do some work here.....
    }
}

/*方案：使用Java的加鎖文件機(jī)制，idea相當(dāng)簡(jiǎn)單，讓運(yùn)行實(shí)例通過(guò)java.nio.channels.FileLock獲得一個(gè)"well-known"文件的互斥鎖。*/
//存在的問(wèn)題：平臺(tái)相關(guān)
import java.io.*;
import java.nio.channels.*;
public class OneInstance_1 {
  public static void main(String[] args) throws Exception {
    FileLock lck = new FileOutputStream("C:\\flagFile").getChannel().tryLock();         
    if(lck == null) {
      System.out.println("A previous instance is already running....");
      System.exit(1);
    }
    System.out.println("This is the first instance of this program...");
    // Do some work here.....
  }
}

//方案3：使用File.createNewFile() and File.deleteOnExit()
//問(wèn)題：文件可能因?yàn)槟承┰虿荒鼙粍h除，即使利用Runtime.addShutdownHook()也有可能產(chǎn)生這種情況。
import java.io.*;
public class OneInstance_3
{
    public static void main(String[] args) throws Exception
    {
        File flagFile = new File("C:\\flagFile");
        if(false == flagFile.createNewFile())
        {
            System.out.println("A previous instance is already running....");
            System.exit(1);
        }
        flagFile.deleteOnExit();
        System.out.println("This is the first instance of this program...");    // Do some work here.....
    }
}

public static void main(String[] args) throws IOException
{ 
    //創(chuàng)建lock.java文件 
    String filePath = new File("IDRCallDll").getAbsolutePath().substring(0, 
            new File("IDRCallDll").getAbsolutePath().lastIndexOf("\\")); 
    File getFile = new File(filePath + "\\" + "lock.java"); 
    System.out.println(getFile.getPath());
 
    //判斷端口是否被占用 
    boolean flag = isLoclePortUsing(20520); 
    System.out.println(flag);
 
    //如果文件存在并且端口被占用則退出 
    if (getFile.exists() && flag)
    {
 
        new MyTray().showDialog(); 
        System.exit(0); 
    }
 
    try
    { 
        Socket sock = new Socket("127.0.0.1", 20520);// 創(chuàng)建socket,連接20520端口 
    }
    catch (Exception e)
    { 
        System.out.println("端口被占用！"); 
    }
 
    final Class<?> clazz = (Class<?>) JavaCall.class; 
    final boolean isWindows = System.getProperty("os.name").contains( 
                                  "Windows"); 
    final List<String> args1 = new ArrayList<String>(); 
    args1.add(isWindows ? "javaw" : "java"); 
    args1.add("-Xmx" + 128 + "M"); 
    args1.add("-cp");
     args1.add(System.getProperty("java.class.path")); 
    args1.add("-Djava.library.path=" 
              + System.getProperty("java.library.path")); 
    args1.add(clazz.getCanonicalName()); 
    // logger.info("start " + args1.toString()); 
    final ProcessBuilder pb = new ProcessBuilder(args1); 
    pb.redirectErrorStream(true);  
    try
    { 
        /**
        * 讀身份證信息程序
        */
 
        pb.start(); 
    }
    catch (Exception e)
    { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
    }  
 
    RandomAccessFile r = new RandomAccessFile( 
        filePath + "\\" + "lock.java", "rws"); 
    FileChannel temp = r.getChannel(); 
    FileLock fl = temp.lock(); 
}
 
/**
* 判斷端口是否被占用
* @param port
* @return
*/
 
public static boolean isLoclePortUsing(int port)
{ 
    boolean flag = true; 
    try
    { 
        flag = isPortUsing("127.0.0.1", port); 
    }
    catch (Exception e)
    { 
    } 
    return flag; 
}
 
public static boolean isPortUsing(String host, int port) throws UnknownHostException
{ 
    boolean flag = false; 
    InetAddress theAddress = InetAddress.getByName(host); 
    System.out.println(theAddress);
 
    try
    { 
        ServerSocket socket = new ServerSocket(port); 
        flag = true; 
    }
    catch (IOException e)
    { 
        System.out.println("beizhanyong"); 
    } 
    return flag; 
}