Why do I get a "dead code" warning in this Java code?

Question

Would someone please tell me why i am getting a dead code warning in the else branch of if (projectId != null) ? If i got this right, the interpreter thinks projectId can never be null - is that right? In my opinion this is not possible...

Integer projectId = null;

if (!sprintTaskConnections.isEmpty())
    projectId = sprintTaskConnections.get(0).getProjectId();

// init name, state, startDate, endDate here

JiraSprint sprint = new JiraSprint(sprintInfo.getInt("id"), name, state, projectId, startDate, endDate);

if (projectId != null)
{
   ...
}

Even if i put a

sprintTaskConnections.add(new JiraSprintTaskConnection(1, 1, 1));

or a

sprintTaskConnections.clear();

in front of

if (!sprintTaskConnections.isEmpty())
projectId = sprintTaskConnections.get(0).getProjectId();

the result is always the same!

Please help me, i just don't get it at the moment!

Canoewood

Who is giving this warning? What interpreter do you mean? – Hindsight

You forgot to turn on the halting problem solver. – Fiendish

Is it just a warning? The checks you are doing seem to be a smart design, so you could possibly just ignore the warning...but I'd need more detail on "if (!sprintTaskConnections.isEmpty())" – Unexampled

@Canoewood But what IDE / compiler are you using? – Serviceberry

Maybe unrelated question, but why bother getting all the config information is the sprintTaskConnections is empty? You would know up front that its just going to fail throw a few lines later anyways... – Fiendish

@Dukeling: I am using the newest version of eclipse. – Canoewood

Answer 1

I don't have the JiraSprint code, so I can't confirm this, but I suspect the JiraSprint constructor takes an int where you pass in the projectId rather than an Integer. That forces Java to auto-unbox the Integer. If the Integer projectId is null, you'll get a NullPointerException (because of the auto-unboxing) there, so you won't even get to the if block. Therefore, projectId must not be null.

Cobbs

This is much more likely actually. +1. – Heteronomous

You're my hero for the day! Thank you! – Canoewood

Answer 2

Maybe: new JiraSprint(..) gets int projectId?

In that case, if projectId is null, this line:

JiraSprint sprint = new JiraSprint(sprintInfo.getInt("id"), name, state, projectId, startDate, endDate);

will throw NPE, so projectId cannot be null after this line.

Martella

Answer 3

projectId has a high chance that it will always be null so the code in the "if" will never get executed

Christiansand

But it's assigned here - projectId = sprintTaskConnections.get(0).getProjectId();. – Serviceberry

only if !sprintTaskConnections.isEmpty() – Christiansand

No, if sprintTaskConnections is not empty, projectId will get a value assigned. – Canoewood

The dead code is the code inside the else part. Aka the compiler thinks projectId will NEVER be null – Besought

You are correct, i was completly missing the point there, TheTerribleSwiftTomato alreay pointed out the not-so-obvious – Christiansand