Common Mistakes To Avoid

❌ Common pitfalls

The following common mistakes should be avoided:

• Forgetting to create the array and only declaring it (int[][] array;)
• Using $1$ as the first index instead of $0$ while accessing rows and/or columns
• Using array.length as the last valid row index instead of array.length - 1
• Using array[0].length as the last valid column index instead of 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)
• Using array.length for both the number of rows and columns

🚨 An important alert

• Do not use initializer syntax, except when declaring the array variable. The following ways are valid:

  Method 1:

  int [][] arr = new int[][]{{1, 2}};
  

  Method 2:

  int [][] arr = {{1, 2}};
  

  Method 3:

  int [][] arr;
  arr = new int[][]{{1, 2}};
  

---