mlk/InstanceLock

Prevents two instances of the same application running at the same time.

Instance Lock

Prevents two instances of the same application from starting.

Usage

Grab the JAR file either manually or via Maven.

<dependencies>
    <dependency>
        <artifactId>InstanceLock</artifactId>
        <groupId>com.github.mlk</groupId>
        <version>1.0</version>
    </dependency>
</dependencies>

Then during application start up create an InstanceLock¹ and check onlyInstance().

InstanceLock lock = new InstanceLock("application_name");
if (!lock.onlyInstance()) {
    // Already running.
    System.exist(-1);
}

If you want the second application to send data to the running application create an ApplicationStartupListener² and pass it into the constructor of the InstanceLock. applicationStartup(String) will be called when a second instance of the application is started. Note: You need to pass a string.

InstanceLock lock = new InstanceLock("application_name",
    new ApplicationStartupListener() {
        @Override
        public void applicationStartup(String message) {
            System.out.println(message);
        }
    });

if (!lock.onlyInstance("message")) {
    // Already running.
    System.exist(-1);
}