title: Java ArrayIndexOutOfBoundsException: 20 multidimensional array
body: <p>I am a new programmer, I have had a class but haven't been back to school yet, so I am trying to get ahead on my own when I have time b doing the problems at projecteuler.net. I have searched on this site and on google for the solution but all of their fixes are using the wrong variable in the for loops which I checked multiple times.</p>
  
  <p>The exception:</p>
  
  <blockquote>
    <p>Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 20
        at Euler11.main(Euler11.java:37)</p>
  </blockquote>
  
  <p>My code:    </p>
  
  <pre><code>public class Euler11 {
      /**
       * @param args
       */
      public static void main(String[] args) {
          int[][] grid = new int[][] {
                  {8, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 2, 12, 50, 77, 91, 8},
                  {49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 04, 56, 62, 00},
                  {81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 03, 49, 13, 36, 65},
                  {52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56, 71, 37, 02, 36, 91},
                  {22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80},
                  {24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50},
                  {32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70},
                  {67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21},
                  {24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72},
                  {21, 36, 23, 9, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33, 97, 34, 31, 33, 95},
                  {78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16, 14, 9, 53, 56, 92},
                  {16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54, 24, 36, 29, 85, 57},
                  {86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58},
                  {19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 04, 89, 55, 40},
                  {04, 52, 8, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66},
                  {88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69},
                  {04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36},
                  {20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 04, 36, 16},
                  {20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 05, 54},
                  {01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 01, 89, 19, 67, 48}
          };  
          long product = 0;
          long hp = 0;
          long vp = 0;
          long d1p = 0;
          long d2p = 0;
  
          for (int h = 3; h &lt; 23; h++) {
              for (int v = 3; v &lt; 23; v++) {
                  hp = grid[h][v] * grid[h][v + 1] * grid[h][v + 2] * grid[h][v + 3];
                  vp = grid[h][v] * grid[h + 1][v] * grid[h + 2][v] * grid[h + 3][v];
                  d1p = grid[h][v] * grid[h + 1][v + 1] * grid[h + 2][v + 2] * grid[h + 3][v + 3];
                  d2p = grid[h][v] * grid[h - 1][v + 1] * grid[h - 2][v + 2] * grid[h - 3][v + 3];
  
                  if (hp &gt; product) {
                      product = hp;
                  }
  
                  if (vp &gt; product) {
                      product = vp;
                  }
  
                  if (d1p &gt; product) {
                      product = d1p;
                  }
  
                  if (d2p &gt; product) {
                      product = d2p;
                  }
              }
          }
      }
  }
  </code></pre>
  
  <p>I apologize for any sloppiness in the code and if you have any advice on that I am always willing to accept criticism.</p>
  
  <p>Looking over the documentation for the ArrayIndexOutOfBoundsException, it mentions negative numbers and &lt;= symbols but I do not have any that I have noticed.</p>
  
  <p>I tried setting h = 0 and v = 0 and having them go to 19 instead of 23 and got the exception but it said -1 instead of 20 and was on line 40. The MultiDimensional array was my friends idea and I feel like there is probably an easier way, but I don't know what it could be so I went with his suggestion. If you have a site that you used to find the answer and could link it I would appreciate it.</p>
  
  <p>Thank you ahead of time for any advice you can give me.</p>