How to optimize java code using the features of java 8

Question

The code below works fine but I want to optimize it and write it in another way.

private List<OrderFeedback> getControlOrderFeedback(List<OrderInner> orderInners){
    List<OrderFeedback> controlResult = new ArrayList();
    if(isTypeDeclaration){
        orderInners.forEach(co -> {
            controlResult.add(OrderFeedback.builder()
                    .result(co.getResult())
                    .code(co.getCode).build()
            );
        });
        return controlResult;
    }
    return null;
}

Answer 1

Not sure what is the bottleneck here but you can rewrite it in a more java-streams fashion like

private List<OrderFeedback> getControlOrderFeedback(List<OrderInner> orderInners){
    if(!isTypeDeclaration) {
        return null;
    }
    return orderInners.stream()
               .map(co -> OrderFeedback.builder().result(OrderInner::getResult).code(OrderInner::getCode).build())
               .collect(Collectors.toList());
}

Note that the only benefit here is that it won't create new ArrayList() unless it passes the isTypeDeclaration check.