Is there a way to take an argument in a callable method?

Question

I have created a piece of code which takes an IP address (from main method in another class) and then loops through a range of IP addresses pinging each one as it goes. I have a GUI front end on this and it was crashing (hence why I've done the multithreading. My problem is I can no longer take the IP address as an argument in my ping code as its callable. I've searched all over for this and cant seem to find a way to get round this. Is there a way for a callable method to take arguments? If not is there any other way to accomplish what I'm trying to do?

sample of my code:

public class doPing implements Callable<String>{

public String call() throws Exception{

    String pingOutput = null;

    //gets IP address and places into new IP object
    InetAddress IPAddress = InetAddress.getByName(IPtoPing);
    //finds if IP is reachable or not. a timeout timer of 3000 milliseconds is set.
    //Results can vary depending on permissions so cmd method of doing this has also been added as backup
    boolean reachable = IPAddress.isReachable(1400);

    if (reachable){
          pingOutput = IPtoPing + " is reachable.\n";
    }else{
        //runs ping command once on the IP address in CMD
        Process ping = Runtime.getRuntime().exec("ping " + IPtoPing + " -n 1 -w 300");
        //reads input from command line
        BufferedReader in = new BufferedReader(new InputStreamReader(ping.getInputStream()));
        String line;
        int lineCount = 0;
        while ((line = in.readLine()) != null) {
            //increase line count to find part of command prompt output that we want
            lineCount++;
            //when line count is 3 print result
            if (lineCount == 3){
                pingOutput = "Ping to " + IPtoPing + ": " + line + "\n";
            }
        }
    }
    return pingOutput;
}
}

IPtoPing used to be the argument that was taken.

Answer 1

You can't pass it as the argument to call() because the method signature doesn't allow it.

However, you can pass it as a constructor argument; e.g.

public class DoPing implements Callable<String>{
    private final String ipToPing;

    public DoPing(String ipToPing) {
        this.ipToPing = ipToPing;
    }

    public String call() throws SomeException {
        InetAddress ipAddress = InetAddress.getByName(ipToPing);
        ....
    }
}

(I've corrected a couple of egregious code style violations!!)

Alternatively, you could:

• declare DoPing as an inner class and have it refer to a final ipToPing in the enclosing scope, or

• add a setIpToPing(String ipToPing) method.

(The last allows a DoPing object to be reused, but the downside is that you will need to synchronize to access it thread-safely.)