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import java.io.File;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
class JustOneLock {
private String appName;
FileLock lock;
FileChannel channel;
public JustOneLock(String appName) {
this.appName = appName;
}
public boolean isAppActive() throws Exception{
File file = new File(System.getProperty("user.home"), appName + ".tmp");
channel = new RandomAccessFile(file, "rw").getChannel();
lock = channel.tryLock();
if (lock == null) {
lock.release();
channel.close();
return true;
}
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
try {
lock.release();
channel.close();
} catch (Exception e) {
e.printStackTrace();
}
}
});
return false;
}
}
public class Main {
public static void main(String[] args)throws Exception {
JustOneLock ua = new JustOneLock("JustOneId");
if (ua.isAppActive()) {
System.out.println("Already active.");
System.exit(1);
} else {
System.out.println("NOT already active.");
}
}
}
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