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Index › Programming Questions & Help › Programs › an array of arraylists

Joe Rice YaBB Newbies Offline Posts: 28

an array of arraylists Apr 7th, 2010, 8:24am   so i am trying to create an array of arraylists and i keep getting a null pointer exception when i try to access them. Code: ArrayList[] blocks = new ArrayList[maxCol]; for(int i = 0; i< maxCol;i++){    for(int x = 0; x< maxRow;x++){      blocks[i].add(new Block(width/2+i*25, height/2+x*25, blocksize, int(random(0,2)), true));    }  } how can i access them if at all possible?

koogy God Member Offline Posts: 788	Re: an array of arraylists Reply #1 - Apr 7th, 2010, 8:34am   you need to initialise each array list, not just the array of them. for(int i = 0; i< maxCol;i++){    blocks[i] = new ArrayList();    for(int x = 0; x< maxRow;x++){      blocks[i].add(new Block(width/2+i*25, height/2+x*25, blocksize, int(random(0,2)), true));    }  }