1Z0-811 Java Basics and Syntax Practice Question
Given: int[] arr = {10,20,30}; System.out.println(arr[3]); What is the result?
⚠ Common exam trap
The trap here is that candidates may forget arrays are zero-indexed and mistakenly think the last element is at index 3, or assume Java returns a default value like 0 for invalid indices.
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
✓
ArrayIndexOutOfBoundsException
Arrays in Java are zero-indexed, so a valid index for an array of length 3 is 0, 1, or 2. Accessing index 3 is out of bounds, causing an ArrayIndexOutOfBoundsException at runtime.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ArrayIndexOutOfBoundsException
Why this is correct
Correct: runtime exception due to invalid index.
- ✗
30
Why it's wrong here
Index 3 is out of bounds.
- ✗
0
Why it's wrong here
No default value; exception thrown.
- ✗
NullPointerException
Why it's wrong here
Array is not null.
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