Code snippet to return the leader node in a Hazelcast cluster.

GetLeaderNode.java

  public boolean isLeader() {
    
    // Get all the Hazelcast instances in the current JVM.
    // In case of carbon server this is always either one 
    // or zero.
    Iterator<HazelcastInstance> iter
                        = Hazelcast.getAllHazelcastInstances().iterator();
    
    if (iter.hasNext()) { // cluster mode 
        HazelcastInstance instance = iter.next();
        return instance.getCluster().getMembers().iterator().next().localMember();
    } else {
        return true; // standalone mode
    }
  }

At the first look this code looks like is doing nothing valuable, but it should work. Please see this thread:
hazelcast/hazelcast#3760

Newer versions should have better ways... Back in the day (around 2015) we had to get the member list and check whether the first member in the list is a local member. if so, that would mean it is the leader. Other option is to try to capture a distributed lock. But it had to be done carefully... had some issues that I can't recall at the moment.