# 10.10. Common Mistakes¶

• forgetting to create the array - only declaring it (int[][] nums;).
• using 1 as the first index not 0 for rows and/or columns.
• using array.length as the last valid row index, not array.length - 1.
• using array[0].length as the last valid column index, not array[0].length - 1.
• using array.length() instead of array.length (not penalized on the free response)
• going out of bounds when looping through an array (using index <= array.length). You will get an ArrayIndexOutOfBoundsException.
• jumping out an loop by using one or more return statements before every value has been processed.
• using the wrong starting and ending indicies on loops.
• using array.length for both the number of rows and columns. Use array[0].length for the number of columns.
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