Can I use static method from a different class?

Question

Below is my CuratorClient class which is connecting to Zookeeper and starting the leader election process as well.

public class CuratorClient {

    // can I make this as static?
    private static CuratorFramework client;
    private String latchPath;
    private String id;
    private LeaderLatch leaderLatch;

    public CuratorClient(String connString, String latchPath, String id) {
        client = CuratorFrameworkFactory.newClient(connString, new ExponentialBackoffRetry(1000, Integer.MAX_VALUE));
        this.id = id;
        this.latchPath = latchPath;
    }

    public void start() throws Exception {
        client.start();
        client.getCuratorClient().blockUntilConnectedOrTimedOut();
        leaderLatch = new LeaderLatch(client, latchPath, id);
        leaderLatch.start();
    }

    public boolean isLeader() {
        return leaderLatch.hasLeadership();
    }

    public Participant currentLeader() throws Exception {
        return leaderLatch.getLeader();
    }

    public void close() throws IOException {
        leaderLatch.close();
        client.close();
    }

    // can I use below method from any other class ?
    protected static List<String> getChildren(String node) throws Exception {
        return client.getChildren().forPath(node);
    }
}

When my service gets started up, in the static block I am making a connection to Zookeeper using CuratorClient and starting the leader election process as well.

public class TestService {

    private static CuratorClient curatorClient = null;
    static {

        try {
            String connectionString = "some-string";
            String hostname = "machineA";

            curatorClient = new CuratorClient(connectionString, "/my/latch", hostname);
            curatorClient.start();

        } catch (Exception ex) {
            // log exception
        }
    }

    ....
    ....

    // some method
    public Map<String, String> installNewSoftware(String node) {

    //.. some other code
    try {
        List<String> children = CuratorClient.getChildren("/my/example");
        System.out.println(children);

    } catch (Exception e) {
        e.printStackTrace();
    }

    //.. some other code
    return null;
    }
}

Now I have some other class as well which likes to use the getChildren method of CuratorClient so in this class, I can directly use like this CuratorClient.getChildren("/my/example"); correct?

public class DifferentClass {

    ....
    ....

    // some new method
    public Map<String, String> installNewSoftware(String node) {
    try {
        List<String> children = CuratorClient.getChildren("/my/example");
        System.out.println(children);

    } catch (Exception e) {
        e.printStackTrace();
    }

    //.. some other code
    return null;
    }
}

In general, this is not a curator question or zookeeper question. It's basically a design question and I am trying to understand whether the way I am doing it will have any problem or not? And I am assuming CuratorFramework will be thread safe as well?

Answer 1

Yes, you can call static methods from other classes.

Your signature looks like this:

protected static List<String> getChildren(String node) throws Exception

The reason you can't call this from another class is because it's protected (visible to the current class and subclasses) instead of public (visible to everywhere).

If you make it visible you can call it with CuratorClient.getChildren().

More information on access modifiers.
More information on class members (static fields).