Optional best practices

Catalog

One Optional What is it?

Two Optional API Introduce

3、 ... and Optional Best practices

3.1 Don't go straight back null, Use Optional.empty();

3.2 Use... Correctly ifPresent()

3.3 To use less get(), multi-purpose orElse() and orElseGet()

3.4 To use less of(), multi-purpose ofNullable()

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One Optional What is it?

Optional The author of Brian Goetz For this API Explanation ：

Our intention was to provide a limited mechanism for library method return types where there needed to be a clear way to represent "no result", and using null for such was overwhelmingly likely to cause errors.

for fear of null The mistake , We provide a finite mechanism for explicitly representing null values .

Optional It's a container , Used to place values that may be empty , It can be handled reasonably and gracefully null.

Two Optional API Introduce

public static<T> Optional<T> empty();  //  Return to one Optional Container object 

public static <T> Optional<T> of(T value); //  Create a Optional object , If  value  yes  null, Throw out  NPE

public static <T> Optional<T> ofNullable(T value); //  Create a Optional object , but  value  Return for space time Optional.empty()

public T get(); //  return Optional The value of the middle package , Before sentencing , Never use directly 

public boolean isPresent(); //  Judge Optional Is there any value in , return  boolean

public void ifPresent(Consumer<? super T> consumer); //  Judge Optional Is there any value in , If there is a value, execute  consumer, Or nothing 

public T orElse(T other); //  return Optional The value of the middle package , But the difference is that when you can't get a value , Return your specified  default

public T orElseGet(Supplier<? extends T> other); //  return Optional The value of the middle package , When the value cannot be obtained , Return your specified  default

public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier); //  return Optional The value of the middle package , Throw the specified exception when the value cannot be obtained 

3、 ... and Optional Best practices

Optional It belongs to the return type , It is usually used in business return value or remote call .

3.1 Don't go straight back null, Use Optional.empty();

//  Use Optional.empty() Before 
private PoiTabHintDTO getPoiTabHintFromTask(FutureTask<PoiTabHintDTO> task) {
    if (Objects.isNull(task)) {
        return null;
    }
    try {
        return ThreadPoolUtils.get(task, 4, TimeUnit.SECONDS);
    } catch (Exception e) {
        log.error("getRdcPoiTabHintFromTask", e);
        Cat.logMetricForCount("getRdcPoiTabHintFromTask");
        return null;
    }
}

//  Use Optional.empty() 
private Optional<PoiTabHintDTO> getPoiTabHintFromTask(FutureTask<Optional<PoiTabHintDTO>> task) {
    if (Objects.isNull(task)) {
        return Optional.empty();
    }
    try {
        return ThreadPoolUtils.get(task, 4, TimeUnit.SECONDS);
    } catch (Exception e) {
        log.error("getRdcPoiTabHintFromTask", e);
        Cat.logMetricForCount("getRdcPoiTabHintFromTask");
        return Optional.empty();
    }
}
//  What needs to be displayed is from optional Get objects from the container , Can reduce NPE The birth of .

3.2 Use... Correctly ifPresent()

//  Use  ifPresent() Before 
if (getPoiTabHintFromTask(rdcPoiHintTask).isPresent()) {
    poiTabHintList.add(getPoiTabHintFromTask(rdcPoiHintTask).get());
}
//  Use  ifPresent()
getPoiTabHintFromTask(rdcPoiHintTask).ifPresent(poiTabHintList::add);

// There's no performance improvement , Code becomes simple .
3.3  To use less  get(), multi-purpose orElse() and orElseGet()
// orElse() Applicable to input parameters are specific values 
public static ConfirmAuthorizationEnum getByCode(int code) {
    return Arrays.stream(ConfirmAuthorizationEnum.values())
        .filter(x -> code == x.getCode())
        .findFirst()
        .orElse(ConfirmAuthorizationEnum.UNINITIALIZED);
}
// orElseGet() Apply to lamda expression 
private Optional<DeliveryReturnBillBO> getReturnBillFromList(
    List<DeliveryReturnBillBO> allDeliveryReturnBillList, String returnBillNo) {
    return Optional.ofNullable(allDeliveryReturnBillList.stream()
        .filter(deliveryReturnBillBO -> returnBillNo.equals(deliveryReturnBillBO.getReturnBillNo()))
        .findFirst()
        .orElseGet(() -> {
            log.error(" No refund order was obtained {} Details of ", returnBillNo);
            Cat.logMetricForCount(DeliveryBill.RELATED_RETURN_BILL_IS_NULL);
            return null;
        }));
}
//  Why use less  get(), It needs to be used in combination with air judgment , This sum !=null It doesn't make much difference .

3.3 To use less get(), multi-purpose orElse() and orElseGet()

// orElse() Applicable to input parameters are specific values 
public static ConfirmAuthorizationEnum getByCode(int code) {
    return Arrays.stream(ConfirmAuthorizationEnum.values())
        .filter(x -> code == x.getCode())
        .findFirst()
        .orElse(ConfirmAuthorizationEnum.UNINITIALIZED);
}
// orElseGet() Apply to lamda expression 
private Optional<DeliveryReturnBillBO> getReturnBillFromList(
    List<DeliveryReturnBillBO> allDeliveryReturnBillList, String returnBillNo) {
    return Optional.ofNullable(allDeliveryReturnBillList.stream()
        .filter(deliveryReturnBillBO -> returnBillNo.equals(deliveryReturnBillBO.getReturnBillNo()))
        .findFirst()
        .orElseGet(() -> {
            log.error(" No refund order was obtained {} Details of ", returnBillNo);
            Cat.logMetricForCount(DeliveryBill.RELATED_RETURN_BILL_IS_NULL);
            return null;
        }));
}
//  Why use less  get(), It needs to be used in combination with air judgment , This sum !=null It doesn't make much difference .

3.4 To use less of(), multi-purpose ofNullable()

//  Use  of() scene 
if (Objects.isNull(returnBillProcessBo)) {
    return Optional.empty();
}
return Optional.of(returnBillProcessBo);

//  Use  ofNullable() scene 
return Optional.ofNullable(returnBillProcessBo);