Using Try Catch Exception handling or explicit checks

Question

I am developing an android service and coming across two different styles to write code to handle validations.

First Style: Using boolean or explicit checks. In this method, I return the whatever values I get from functions. Returned values could be null, Closed (not valid).

boolean fbConnected = appPrefences.isFBConnected();
if (!fbConnected)
{
    ShowNotification("FB not connected");
    stopSelf();
    return;
}

Session session = GetSession();
if (session.isClosed())
{
    ShowNotification("Session not valid");
    stopSelf();
    return;
}

Coordinates result = getLocation();
if(result == null)
{
    ShowNotification("Could not get location");
    stopSelf();
    return;
}

//  Do something finally with Session, FB and location

Second Style: Using Exception handling. Here, I throw my own custom exception from utility methods if the session is closed (invalid) or if the location is null. And I handle it as follows:

try
{
    appPrefences.connectToFb();
    Session session = GetSession();
    Coordinates result = getLocation();
}
catch(FBException e)
{
    ShowNotification("FB not connected");
    stopSelf();
    return;
}
catch(SessionException e)
{
    ShowNotification("Session not valid");
    stopSelf();
    return;
}
catch(LocationException e)
{
    ShowNotification("Could not get location");
    stopSelf();
    return;

}

//  Do something finally with Session, FB and location

In my view the first one is better, for the reason below:

• In second method, Throwing exceptions incurs performance hits.

Is it OK to use the first method or there are some real benefits to use the second method ?

Answer 1

Use exceptions to

• signal that the caller violates the preconditions for calling the function. This should usually lead to a fix in the programm, because it is the responsibility of the caller to ensure that the preconditions are met.

• signal that the postconditions cannot be ensured by the function despite the fact that the preconditions for calling the function are fulfilled. This should be handled gracefully by the caller.

I think a function like isFBConnected should check whether facebook is connected. There are two perfectly valid answers: Yes, No. An exception should be thrown if the function is not able to determine whether facebook is connected.

Answer 2

The use of try/catch blocks in normal program flow incurs a performance hit. It's better to use the if/then statements in the first example.

https://softwareengineering.stackexchange.com/questions/189222/are-exceptions-as-control-flow-considered-a-serious-antipattern-if-so-why

This is mentioned in Effective Java. Exceptions are, as their name implies, to be used only for exceptional conditions; they should never be used for ordinary control flow.