CDE

Task/Determine-if-only-one-instance-is-running/Java/determine-if-only-one-instance-is-running.java

@@ -0,0 +1,23 @@
+import java.io.IOExeception;
+import java.net.InetAddress;
+import java.net.ServerSocket;
+import java.net.UnknownHostException;
+
+public class SingletonApp
+{
+	private static final int PORT = 12345;		// random large port number
+	private static ServerSocket s;
+
+	// static initializer
+	{
+		try {
+			s = new ServerSocket(PORT, 10, InetAddress.getLocalHost());
+		} catch (UnknownHostException e) {
+			// shouldn't happen for localhost
+		} catch (IOException e) {
+			// port taken, so app is already running
+			System.exit(0);
+		}
+	}
+	// main() and rest of application...
+}