How can i view the output of a system call in java? [closed]

Im writing a java program that will scan a range of IP addresses with namp. The code isn't complete and there are a few issues i know i need to work though, so keep that in mind.

What i cant seem to figure out right now is how to view the output of of my nmap scan.

Right now the program will loop though 192.168.0.0 - 192.168.255.255 (infinitely, until i fix it) as confirmed with the system.out.println that's commented out. After that i run namp on the addresses but don't get any output. Ideas?

Below is the chunk of code with the nmap scan, its the first case in my switch statement:

case 1:
    IP = "192.168.";
    for (int i = 0; i < oct[1].length; i++) {
        for (int p = 0; p < oct[2].length; p++) {
            String addr = IP + 1 + "." + p;
//                  System.out.println(addr);

            Runtime aRT = Runtime.getRuntime();
            Process aProc = aRT.exec("/usr/local/bin/nmap -sn -n" + addr);
            //
            // HOW TO I VIEW THE RESULTS OF NMAP
            //
        }
    }

    break;

And here is the entire program thus far. Everything is in one class right now, i'll break it up later.

public class Start {
public static void main(String args[]) throws IOException {


    String s1 = getInput("Please select and IP range to scan: \n" + "\n" + 
            "1) 192.168.\n" + 
            "2) 172.28.\n" + 
            "3) 10.\n" 
            + "\n" + ":: ");

    int i1 = Integer.parseInt(s1);

    String IP = "";
    int oct[][] = new int[256][256];

    switch (i1) {
    case 1:
        IP = "192.168.";
        for (int i = 0; i < oct[1].length; i++) {
            for (int p = 0; p < oct[2].length; p++) {
                String addr = IP + 1 + "." + p;
//                  System.out.println(addr);

                Runtime aRT = Runtime.getRuntime();
                Process aProc = aRT.exec("/usr/local/bin/nmap -sn -n" + addr);
                //
                // HOW TO I VIEW THE RESULTS OF NMAP
                //
            }
        }

        break;
    case 2:

        System.out.println("case2");
        break;
    case 3:

        System.out.println("case3");
        break;
    case 99:

        System.out.println("case99");
        break;
    default:
        System.out.println("default");
        break;
    }



}
private static String getInput(String prompt) {
    BufferedReader stdin = new BufferedReader(
            new InputStreamReader(System.in));

    System.out.print(prompt);
    System.out.flush();

    try {
        return stdin.readLine();
    } catch (Exception e) {
        return "Error: " + e.getMessage();
    }
}

}