Java programs start only once on a computer, only one process is opened

Scenario 1:

A single-process program can be bound with a port. When the program starts, you can try to see if the port is already in use, and if so, the program has started.

Scenario 2:
You can create a hidden file in a Java program and delete the file when the program exits. This way, when the program starts, you determine if the file exists, if the description is already started.

Import Java.io.file;import java.io.ioexception;import Java.io.randomaccessfile;import java.nio.channels.FileLock;/    * * Filelockmanager file Lock Management * */public class Filelockmanager {private Filelock filelock = null;    Private file File = null;    Private Randomaccessfile randomaccessfile = null;    Public Filelockmanager (String filename) {this.file = new file (filename);    Public Filelockmanager (file file) {this.file = file;  /** * file Lock and create file * * @return * @throws IOException */public Boolean lock () throws IOException            {if (!this.file.exists ()) {this.file.createNewFile ();            This.randomaccessfile = new Randomaccessfile (this.file, "RW");            This.filelock = This.randomAccessFile.getChannel (). Trylock ();            if (This.fileLock.isValid ()) {return true;            } else {return false;        }} else {return false; }}/** * Unlock and deleteFILE * * @return * @throws IOException */public Boolean unLock () throws IOException {if (!this.        File.exists ()) {return true;            } else {if (this.filelock! = null) {this.fileLock.release ();            } if (this.randomaccessfile! = null) {this.randomAccessFile.close ();            } if (This.file.delete ()) {return true;            } else {return false;     }}}/** * @return Returns the Filelock.    */Public Filelock Getfilelock () {return this.filelock;     }/** * @param filelock * The Filelock to set.    */public void Setfilelock (Filelock filelock) {this.filelock = Filelock; }}

Java programs start only once on a computer, only one process is opened