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);
    }

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 ...

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 ...

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

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 ...

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

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.