import java.io.IOException;
import java.net.InetAddress;
import java.util.*;

public class HostInfo {

    public static void main(String[] args) throws Exception {
        String regex = "^(java\\.version)|(os\\.name)$";
        if (args.length > 0) {
            regex = args[0];
        }
        List<String> keys = new ArrayList<>(System.getProperties().stringPropertyNames());
        Collections.sort(keys);
        for (String key : keys) {
            if (key.matches(regex)) {
                System.out.format("%s=%s%n", key, System.getProperty(key));
            }
        }
        InetAddress address = InetAddress.getLocalHost();
        System.out.format("InetAddress.getLocalHost() = %s%n", address);
    }

}