我们目前有以下复合 if 语句...

if ((billingRemoteService == null)
    || billingRemoteService.getServiceHeader() == null
    || !"00".equals(billingRemoteService.getServiceHeader().getStatusCode())
    || (billingRemoteService.getServiceBody() == null) 
    || (billingRemoteService.getServiceBody().getServiceResponse() == null) 
    || (billingRemoteService.getServiceBody().getServiceResponse().getCustomersList() == null) 
    || (billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList() == null) 
    || (billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList().get(0) == null) 
    || (billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList().get(0).getBillAccountInfo() == null)
    || (billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList().get(0).getBillAccountInfo().getEcpdId() == null)) {
        throw new WebservicesException("Failed to get information for Account Number " + accountNo);
}

return billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList().get(0);

try {
    //Check to be sure there is an EpcdId.
    (billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList().get(0).getBillAccountInfo().getEcpdId();
    return billingRemoteService.getServiceBody().getServiceResponse().getCustomersList().getCustomersList().get(0);
} catch (NullPointerException npe) {
    throw new WebservicesException("Failed to get information for Account Number " + accountNo);
}

最佳答案

我必须不同意埃德温巴克的论点。

他说:

As others have stated, exceptions are more expensive than if statements. However, there is an excellent reason not to use them in your case. "Exceptions are for exceptional events"

When unpacking a message, something not being in the message is expected error checking, not an exceptional event.

If the probability of the event is P

• the average cost of using exceptions is:

  P * cost of an exception being created/thrown/caught/handled + (1 - P) * cost of no explicit tests

• the average cost of not using exceptions is:

  P * cost testing for the condition when it occurs and doing the error handling + (1 - P) * cost of testing when the condition doesn't occur.

  // Version 1
  if (someTest()) {
      doIt();
  } else {
      recover();
  }

  // Version 2
  try {
      doIt();
  } catch (SomeException ex) {
      recover();
  }

  V1 = cost("someTest") + P * cost("recover") + (1 - P) * cost("doIt-success")

  v2 = P * ( cost("doit-fail") + cost("throw/catch") + cost("recover") ) +
       (1 - P) * cost("doIt-success")

  V1 - V2 = cost("someTest") + P * cost("recover") + 
            (1 - P) * cost("doIt-success") -
            P * cost("doit-fail") - P * cost("throw/catch") -
            P * cost("recover") - (1 - P) * cost("doIt-success")

          = cost("someTest") - P * ( cost("doit-fail") + cost("throw/catch") )

The real reason you shouldn't catch unchecked exceptions for flow control is this: what happens if one of the methods you call throws an NPE? You catching the NPE assumes that it came from your code when it may have come from one of the getters. You may be hiding a bug underneath the code and this can lead to massive debugging headaches (personal experience). Performance arguments are useless when you might be hiding bugs in your (or others') code by catching an unchecked exception like NPE or IOOBE for flow control.

关于java - Java 6 中 if/or 与 try/catch 的复合成本，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12358686/