Array Index Out Of Bounds - Java

Question

I have started to work on my first Java program, which is a simple calculator, however I get an error claiming that my array is out of bounds. I have tried to debug it to see wh

Answer 1

When operationIndex is equal to the last element index in outputNum, then operationIndex + 1 will be greater than the last element index: hence your exception

You would be better off using a for loop that started at index 1, and doing:

// assuming that operationList and outputNum always 
//   have the same number of elements
for (int i = 1; i < operationList.size(); i++) {
  ...
  answer = outputNum.get(i - 1) * outputNum.get(i);
  ...
}

or, alternatively, use your current loop, but do:

  // operationIndex++; // remove this and use ..
  if (++operationIndex >= outputNum.size()) break;

Answer 2

You are only ever adding one item to your list:

currentNum = Double.parseDouble(currentString);
outputNum.add(currentNum);

Then you try to access what seems to be a second object at index operationindex +1 which doesn't exist:

answer = outputNum.get(operationIndex) * outputNum.get(operationIndex+1);