How to Fix ArrayIndexOutOfBoundsException in Java Loops
This 1Z0-811 practice question tests your understanding of arrays and methods. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds for length 5
at ArrayExample.main(ArrayExample.java:6)
Refer to the exhibit. The code at line 6 of ArrayExample.java is: int[] arr = {10, 20, 30, 40, 50}; int sum = 0; for (int i = 0; i <= arr.length; i++) sum += arr[i]; Which change fixes the exception?
Exhibit
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds for length 5
at ArrayExample.main(ArrayExample.java:6)
A
Change array declaration to int[] arr = new int[6];
Why wrong: Changing the array declaration to int[] arr = new int[6]; does not fix the exception because the loop still iterates up to index 5, causing an ArrayIndexOutOfBoundsException. The array initializer still has 5 elements, so arr[5] is out of bounds.
B
Change loop initialization to i = 1
Why wrong: Changing the loop initialization to i = 1 avoids the exception for index 0, but still causes an exception when i reaches arr.length (5). The loop condition is still i <= arr.length, so it will attempt arr[5] and throw an ArrayIndexOutOfBoundsException.
C
Change loop condition to i < arr.length
Changing the loop condition to i < arr.length ensures that the loop runs only for indices 0 through arr.length-1 (0-4), which are all valid. This correctly fixes the off-by-one error and prevents the ArrayIndexOutOfBoundsException.
D
Change arr.length to arr.length - 1
Why wrong: Changing arr.length to arr.length - 1 in the condition results in i <= arr.length - 1, which does technically fix the exception for this specific array, but it is not the recommended fix because it still uses the <= operator and can be confusing. The standard approach is to use i < arr.length. Additionally, if the array length were zero, this condition would not work properly. Therefore, option D is considered incorrect in this exam.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change loop condition to i < arr.length
The exception occurs because the loop condition `i <= arr.length` causes the loop to iterate one index beyond the array's last valid index (arr.length - 1). When `i` equals `arr.length` (5), `arr[5]` is accessed, which throws an ArrayIndexOutOfBoundsException. Changing the condition to `i < arr.length` ensures the loop runs only for indices 0 through 4, fixing the exception. Option D, changing `arr.length` to `arr.length - 1` in the condition, also technically fixes the exception, but it is not the standard or recommended fix; the intended correct answer is to use the `<` operator.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Change array declaration to int[] arr = new int[6];
Why it's wrong here
Changing the array declaration to int[] arr = new int[6]; does not fix the exception because the loop still iterates up to index 5, causing an ArrayIndexOutOfBoundsException. The array initializer still has 5 elements, so arr[5] is out of bounds.
✗
Change loop initialization to i = 1
Why it's wrong here
Changing the loop initialization to i = 1 avoids the exception for index 0, but still causes an exception when i reaches arr.length (5). The loop condition is still i <= arr.length, so it will attempt arr[5] and throw an ArrayIndexOutOfBoundsException.
✓
Change loop condition to i < arr.length
Why this is correct
Changing the loop condition to i < arr.length ensures that the loop runs only for indices 0 through arr.length-1 (0-4), which are all valid. This correctly fixes the off-by-one error and prevents the ArrayIndexOutOfBoundsException.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change arr.length to arr.length - 1
Why it's wrong here
Changing arr.length to arr.length - 1 in the condition results in i <= arr.length - 1, which does technically fix the exception for this specific array, but it is not the recommended fix because it still uses the <= operator and can be confusing. The standard approach is to use i < arr.length. Additionally, if the array length were zero, this condition would not work properly. Therefore, option D is considered incorrect in this exam.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The most common mistake in array iteration is using `<=` instead of `<`. Since arrays are zero-indexed, the last valid index is `arr.length - 1`. Using `<=` with array length causes an `ArrayIndexOutOfBoundsException` because it tries to access `arr[arr.length]`.
Trap categories for this question
Similar concept trap
Changing arr.length to arr.length - 1 in the condition results in i <= arr.length - 1, which does technically fix the exception for this specific array, but it is not the recommended fix because it still uses the <= operator and can be confusing. The standard approach is to use i < arr.length. Additionally, if the array length were zero, this condition would not work properly. Therefore, option D is considered incorrect in this exam.
Detailed technical explanation
How to think about this question
In Java, arrays are zero-indexed, so valid indices range from 0 to arr.length - 1. The ArrayIndexOutOfBoundsException is a runtime exception thrown by the JVM when an array is accessed with an illegal index. The loop condition `i < arr.length` is the idiomatic way to iterate over all elements without exceeding bounds, and it is a common pattern in for-each loops and manual iteration. Under the hood, the JVM checks array bounds on every access, and violating them throws the exception immediately.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 1Z0-811 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Arrays and Methods — This question tests Arrays and Methods — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change loop condition to i < arr.length — The exception occurs because the loop condition `i <= arr.length` causes the loop to iterate one index beyond the array's last valid index (arr.length - 1). When `i` equals `arr.length` (5), `arr[5]` is accessed, which throws an ArrayIndexOutOfBoundsException. Changing the condition to `i < arr.length` ensures the loop runs only for indices 0 through 4, fixing the exception. Option D, changing `arr.length` to `arr.length - 1` in the condition, also technically fixes the exception, but it is not the standard or recommended fix; the intended correct answer is to use the `<` operator.
What should I do if I get this 1Z0-811 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Variation 1. Consider the following code:
int[] arr = new int[5];
for (int i = 0; i <= arr.length; i++) {
arr[i] = i;
}
System.out.println(arr[0]);
What is the result?
medium
A.0
B.5
C.4
✓ D.An ArrayIndexOutOfBoundsException is thrown.
Why D: The correct answer is D because the loop condition `i <= arr.length` causes `i` to iterate from 0 to 5 inclusive. Since `arr` has indices 0 through 4, accessing `arr[5]` throws an `ArrayIndexOutOfBoundsException`. The exception occurs before `arr[0]` can be printed.
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Question Discussion
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