[1.12.x/1.11.x] [SOLVED] hasCapability NPE

[Bektor]

Hi,

 

I'm wondering how I can work around an NPE caused by tile.hasCapability(CapabilityEnergy.ENERGY, (EnumFacing) null). 

The code there should actually check if the TileEntity has the capability at all without taking care of the sides. (thus all sides are checked first and then the side null at last)

 

Reasons for having the null check there:

On 4/19/2017 at 10:50 PM, diesieben07 said:

• You might want to call getCapability with side null, too.

On 4/19/2017 at 11:22 PM, diesieben07 said:

Because the capability might be exposed with side null and not any specific side. In that case your pipe would ignore that capability.

 

 

Thx in advance.

Bektor

Edited October 2, 2017 by Bektor

[Draco18s]

*Looks for code*

*Fails to find code*

*Hits "back" on browser*

[Bektor]

3 minutes ago, Draco18s said:

*Looks for code*

*Fails to find code*

*Hits "back" on browser*

I just copied the one line into the post, but here is the complete method. Arguments used: the tilenentity, null

    public static boolean hasCapability(TileEntity tile, EnumFacing orientation) {
    	EnumFacing side = orientation != null ? orientation.getOpposite() : (EnumFacing) null;
    	
    	if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;
    	else if(TeslaHelper.isEnergyHolder(tile, side)) return true;
    	else if(TeslaHelper.isEnergyProducer(tile, side)) return true;
    	else if(TeslaHelper.isEnergyReceiver(tile, side)) return true;
    	
    	return false;
    }

[Draco18s]

14 minutes ago, Bektor said:

I just copied the one line into the post, but here is the complete method. Arguments used: the tilenentity, null

    public static boolean hasCapability(TileEntity tile, EnumFacing orientation) {
    	EnumFacing side = orientation != null ? orientation.getOpposite() : (EnumFacing) null;
    	
    	if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;
    	else if(TeslaHelper.isEnergyHolder(tile, side)) return true;
    	else if(TeslaHelper.isEnergyProducer(tile, side)) return true;
    	else if(TeslaHelper.isEnergyReceiver(tile, side)) return true;
    	
    	return false;
    }

 

Uh...

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

[Choonster]

Where is the exception being thrown?

 

Is it being thrown on the line that calls TileEntity#hasCapability or is it being thrown inside TileEntity#hasCapability?

 

Post the stacktrace.

[Bektor]

6 minutes ago, Draco18s said:

 

Uh...

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Let me dive into that...

orientation.getOpposite()

if(tile.hasCapability(CapabilityEnergy.ENERGY, orientation)) return true;

Ok.... wtf have I done there.... Must have been one of these midnight programming nights. ^^

[LexManos]

You need to post the full code context, and the exceptions.

We dont know whats erroing if you dont give us the context.

As for @Draco18s Its not recursive, thats a static function.

But yes we dont have enough information, so post your logs, post your code, post everything even remotely related.

[Draco18s]

1 minute ago, LexManos said:

As for @Draco18s Its not recursive, thats a static function.

But yes we dont have enough information, so post your logs, post your code, post everything even remotely related.

You're right, I assumed it was the tile's own hasCap function.

[Bektor]

16 hours ago, Draco18s said:

You're right, I assumed it was the tile's own hasCap function.

It wasn't the tiles own capability function. It is a method which should check if a given tile entity has the capability at the given orientation.

The method is used when for example a cable or a machine or whatever wants the send energy, but beforehand make sure that the block

to which the energy should be send even got the capability. 

Thought in your second answer I noticed that some variable moved to some place it was never supposed to be in the first place.

The variable side should be used in the if-statement like in all other statements, but it was not which resulted into the crash

 as the variable orientation got never casted to EnumFacing if it was null. Thought in my opinion null is still null, but without the cast it seems

like it is not quite null (I don't know the internal processing there).

So using the side variable which should have been used (and probalby was before some internal code iterations) solves the problem.

Edited October 3, 2017 by Bektor

[Draco18s]

25 minutes ago, Bektor said:

Thought in my opinion null is still null, but without the cast it seems like it is not quite null (I don't know the internal processing there).

The casting is there for the compiler. Null is still null, but because null can "be" anything, you have to cast it to a type.

[Bektor]

1 minute ago, Draco18s said:

The casting is there for the compiler. Null is still null, but because null can "be" anything, you have to cast it to a type.

What do you mean by null is there for the compiler? I am wondering why the compiler just doesn't cast it then automatically to the correct type

(I know C++ can do this, but don't ask me in which cases C++ will do this automatically ^^)

Also if null can be anything, how does it work to check if an object is null or not if it can be anything. Thought I'm wondering what this in memory actually

is if it can be anything. Will the PC just say, ok there you go, take this bit of RAM with whatever might be left in there and let it be null.

[Bektor]

13 minutes ago, diesieben07 said:

If you store an object in a variable, you are not storing that object, you are storing a reference to that object

Which sounds like C++ and not Java. ^^

13 minutes ago, diesieben07 said:

null is just a fancy name for "the address 0".

meaning nullptr

 

I somehow have the feeling that all this Java pointers do not exists there and all of that stuff just makes it more

complicated to understand.

In my brain its just somehow programmed: Java "no" real pointers, C++ pointers

[Bektor]

Just now, diesieben07 said:

Java is not magic. It does the same thing under the hood, it just hides it in a layer of abstraction and type-safety checks.

 

Yeah, I know. But if feels somehow as if this makes it more complicated to understand the null stuff.

I mean, I know that null has to be casted in this case. Thought I never really thought about C++ nullptr.

It's there and that's all I've ever thought about. What it is and all that stuff is the same with Java null, I've

just used it like null means nothing assigned to the value. What this nothing is, that's something I've never learned

in school nor is it written in any of my Java books and C++ nullptr, might be that it is better described when I

get to the point where it is explained. ^^

 

6 minutes ago, diesieben07 said:

Java stuff under the hood uses the same pointers C or C++ does.

Which makes sense as if I recall correctly the Java compiler is written in C++ and code of the java API itself references through JNI to C++ stuff?

Thought I know for sure that LWJGL does this.

I guess when I've got more time I'll look into VS memory display to see what nullptr is there exactly.

[Bektor]

18 minutes ago, diesieben07 said:

Java variables that store objects are references

Yeah, but all of this null stuff. I've got the feeling you know more about it then the ones who wrote the books I read a long time ago. (Starting with some Java for kids books and later books for adults)

I guess it is better explained in books like "Java ist auch eine Insel", but I've never read those books as most of the Java features those books covered I already learned

and I got interested in programming and thus started learning Java even before I could understand English or played Minecraft.

Edited October 3, 2017 by Bektor