Try-Catch, optional/null, and lambda

Question

考虑以下代码：

• OBJ在通过服务进行INTIAL后未经修改，但是由于尝试/捕获块，因此并未被认为是有效的。有没有办法避免这种情况？

• 是否可以将可选的视为视为避免零检查的通用方法？在此示例中，服务会抛出异常或返回null，还是始终返回可选？

  //to be used outside try/catch block, object must be initialized as null
  SomeObject obj = null;
  try {
      obj = someService.getSomeObject();
  } catch (ServiceException e) {
      LOG.error("Something nasty happened", e);
  }
  //the service could have returned a null object
  if(obj == null) {
      LOG.error("Obj is null");
  }
  //to be used in a lambda, object must be final
  SomeObject objCopy = obj;
  boolean test = someList.stream()
          .anyMatch(o->o.equals(objCopy));
  

Answer 1

只是将尝试/捕捉到单独的方法（这通常是很好的做法，因为它使代码更可读。请参阅Robert Cecil Martin的" Clean Code"）

final Optional<SomeObject> obj = getObjFromService(someService);

...

private Optional<SomeObject> getObjFromService(Service someService) {
    try {
        return Optional.of(someService.getSomeObject());
    } catch (ServiceException e) {
        LOG.error("Something nasty happened", e);
    }
    return Optional.empty();
}

您也可以从方法getObjFromService返回null，您仍然可以声明变量最终，因为您仅分配了一次。

Answer 2

使objcopy final

final SomeObject objCopy = obj;
boolean test = someList.stream()
    .anyMatch(o->o.equals(objCopy));