Unknown null pointer error

[endershadow]

when I place the block, the game crashes and gives a null pointer exception. I'm not sure why it does that, but here's the method where it occurs.

@Override
public void onBlockAdded(World world, int x, int y, int z)
    {
	int randBlock = rand.nextInt(Block.blocksList.length);
	world.setBlock(x, y, z, Block.blocksList[randBlock].blockID);
    }

[RANKSHANK]

I'm guessing (not enough code for any other guesses) that you didnt instantiate that random, or it could be that your random is pulling null  blocks from the block list ...

[Torojima]

since you have not supplied the crash report everything we can do is guessing ... but the obvious solution would be this:

public void onBlockAdded(World world, int x, int y, int z)
{
int randBlock = rand.nextInt(Block.blocksList.length);
if(null != Block.blocksList[randBlock])
{
	world.setBlock(x, y, z, Block.blocksList[randBlock].blockID);
}
}

 

you very obviously presume every BlockId is available, which also very obviously is not the case. Thus when your random number hits an empty spot, there probably will be a null stored at that place...

 

As a general rule for coding you should remember *never* to access anything you haven't checked before or are very (rather absolutely) certain, is properly filled ...

[jordan30001]

note a block can be null but still contain a block

 

for instance redpower blocks are all stored as null but they are actually not null

[Torojima]

  On 5/4/2013 at 8:20 AM, jordan30001 said:

note a block can be null but still contain a block

 

for instance redpower blocks are all stored as null but they are actually not null

 

they are stored as null in the Block.blocklist? I haven't checked, but frankly can not believe that ...

[RANKSHANK]

  On 5/4/2013 at 8:20 AM, jordan30001 said:

note a block can be null but still contain a block

 

for instance redpower blocks are all stored as null but they are actually not null

Not possible;

 

 

and you're better with a loop which is a bit process intensive if this is done often, or creating an array of possible values at the post init

public static int[] possible;
public void storage(){
public List<Integer> pV = new ArrayList();
for(Block b : Block.blockList)
if(b!=null)
pV.add(b.blockId);
int a = -1;
possible = new int[pV.size()];
for(int i : pV)
possible[a++] = i;
}

and then select from that

[endershadow]

thanks everyone for your help. I wrote that code at 12 midngiht after a long day and only 5 hours of sleep the night before.