# V6025. Possibly index is out of bound.

When indexing into a variable of type 'array', 'list', or 'string', an 'IndexOutOfBoundsException' exception may be thrown if the index value is outbound the valid range. The analyzer can detect some of such errors.

For example, it may happen when iterating through an array in a loop:

    int[] buff = new int[25];
    for (int i = 0; i <= 25; i++)
      buff[i] = 10;

Keep in mind that the first item's index is 0 and the last item's index is the array size minus one. Fixed code:

    int[] buff = new int[25];
    for (int i = 0; i < 25; i++)
      buff[i] = 10;

Errors like that are found not only in loops but in conditions with incorrect index checks as well:

    void ProcessOperandTypes(int opCodeValue, byte operandType)
    {
      byte[] OneByteOperandTypes = new byte[0xff];
      if (opCodeValue < 0x100)
      {
        OneByteOperandTypes[opCodeValue] = operandType;
      }
      ...
    }

Fixed version:

    void ProcessOperandTypes(int opCodeValue, byte operandType)
    {
      byte[] OneByteOperandTypes = new byte[0xff];
      if (opCodeValue < 0xff)
      {
        OneByteOperandTypes[opCodeValue] = operandType;
      }
      ...
    }

Programmers also make mistakes of this type when accessing a particular item of an array or list.

    private Map<String, String> TransformListToMap(List<String> config)
    {
      Map<String, String> map = new HashMap<>();
      if (config.size() == 10)
      {
        map.put("Base State", config.get(0));
        ...
        map.put("Sorted Descending Header Style", config.get(10));
      }
      ...
      return map;
    }

In this example, the programmer made a mistake in the number of entries in the 'config' list. The fixed version should look like this:

    private Map<String, String> TransformListToMap(List<String> config)
    {
      Map<String, String> map = new HashMap<>();
      if (config.size() == 11)
      {
        map.put("Base State", config.get(0));
        ...
        map.put("Sorted Descending Header Style", config.get(10));
      }
      ...
      return map;
    }

This diagnostic is classified as:

CWE-125 CWE-787

You can look at examples of errors detected by the V6025 diagnostic.