1Z0-811 Control Flow and Loops Practice Question
A developer is writing a method to find the first occurrence of a negative number in an array and return its index, or -1 if none found. The current implementation uses a for loop with an if condition and a return when found. However, the method throws a NullPointerException when the array is null. The developer wants to handle this edge case gracefully and still return -1. Which approach is most appropriate?
⚠ Common exam trap
Oracle often tests the misconception that a null check inside a loop (or using a try-catch) can handle a null array, but the NullPointerException occurs before the loop body executes, making any inside-loop handling ineffective.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a null check at the beginning of the method and return -1 if null
It directly checks if the array reference is null before any iteration, returning -1 immediately. This is the simplest and most efficient way to handle a null input, avoiding any attempt to access the array's length or elements, which would throw a NullPointerException. The method's contract is preserved by returning -1 when no negative number is found, including the case of a null array.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Add a null check at the beginning of the method and return -1 if null
Why this is correct
This handles the null case elegantly and prevents the exception.
- ✗
Use an enhanced for loop with a null check
Why it's wrong here
An enhanced for loop also fails with a null array as it requires a non-null reference to iterate.
- ✗
Use a try-catch block inside the loop
Why it's wrong here
This is inefficient and poor practice; it's better to check upfront.
- ✗
Use a while loop with a null check inside
Why it's wrong here
Accessing the array's length or elements would cause NullPointerException before the null check if the array is null.
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