polkawebj-sample001.java

    public void run1(String endPoint) {
        WsProvider wsProvider = new WsProvider(endPoint);
        Promise<ApiPromise> ready = ApiPromise.create(wsProvider);
        
        IRpcFunction.Unsubscribe<Promise> unsubscribeHandler = null;
        ready.then( (ApiPromise api) -> {
            Promise<IRpcFunction.Unsubscribe<Promise>> invoke = api.rpc().chain().function("subscribeNewHead").invoke(
                    (IRpcFunction.SubscribeCallback<Header>) (Header header) ->
                    {
                        System.out.println("Chain is at block: " + header.getBlockNumber()+" trigger "+count);
                        count++;
                        if (count >5) {
                            unsubscribeHandler.unsubscribe();
                        }
                    });
            return invoke;
        }).then((IRpcFunction.Unsubscribe<Promise> result) -> {
            // Results in compile error: "Variable used in lambda expression should be final or effectively final
            unsubscribeHandler =result;
            return null;
        })._catch((err) -> {
            err.printStackTrace();
            return Promise.value(err);
        });
        try {
            Thread.sleep(20000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

This results in a compile error on line 19. A local variable out-of-scope of the lambda expression must be final.