The correct fix is to change the loop condition to i < arr.length. This resolves the ArrayIndexOutOfBoundsException because the original condition, likely i <= arr.length, allows the loop to access an index equal to the array’s length, which is always out of bounds since valid indices run from 0 to arr.length - 1. By using the strict less-than operator, the loop stops before reaching that invalid index, ensuring every iteration accesses a valid element. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this tests your understanding of zero-based indexing and loop boundary conditions—a classic trap where developers mistakenly use <= instead of <. Remember the memory tip: “Less than length keeps you in bounds; less than or equal sends you over the edge.”
1Z0-829 Controlling Program Flow Practice Question
This 1Z0-829 practice question tests your understanding of controlling program flow. 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
Refer to the exhibit.
```
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 3
at LoopExample.main(LoopExample.java:5)
```
Source code of LoopExample.java:
```java
1: public class LoopExample {
2: public static void main(String[] args) {
3: int[] arr = {1,2,3};
4: for (int i = 0; i <= arr.length; i++) {
5: System.out.println(arr[i]);
6: }
7: }
8: }
```
Refer to the exhibit.
```
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 3
at LoopExample.main(LoopExample.java:5)
```
Source code of LoopExample.java:
```java
1: public class LoopExample {
2: public static void main(String[] args) {
3: int[] arr = {1,2,3};
4: for (int i = 0; i <= arr.length; i++) {
5: System.out.println(arr[i]);
6: }
7: }
8: }
```
A
Change line 4 to: for (int i = 0; i < arr.length; i++)
Corrects the off-by-one error.
B
Change line 4 to: for (int i = 1; i <= arr.length; i++)
Why wrong: Starts at 1, misses arr[0] and still out of bounds at i=3.
C
Change line 4 to: for (int i = 0; i <= arr.length-1; i++)
Why wrong: Valid but unnecessarily complex; i<arr.length is simpler.
D
Change line 5 to: System.out.println(arr[i-1]);
Why wrong: Would print wrong elements and still go out of bounds for i=3? Actually i<=3, i=3: arr[2] okay, but i=3 still accesses arr[2]? No, i=3 arr[2] works but loop still goes to i=3? Wait line 4 condition i<=arr.length, with arr.length=3, i runs 0,1,2,3. i=3: arr[3] out of bounds. Changing to arr[i-1] would cause i=0 arr[-1] exception earlier. So not valid.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change line 4 to: for (int i = 0; i < arr.length; i++)
Option A is correct because it changes the loop to start at index 0 and continue while i < arr.length, which correctly iterates over all valid indices (0 to arr.length-1). The original code likely used i <= arr.length, causing an ArrayIndexOutOfBoundsException when accessing arr[i] at i = arr.length. By using i < arr.length, the loop stops before reaching the out-of-bounds index.
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 line 4 to: for (int i = 0; i < arr.length; i++)
Why this is correct
Corrects the off-by-one error.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change line 4 to: for (int i = 1; i <= arr.length; i++)
Why it's wrong here
Starts at 1, misses arr[0] and still out of bounds at i=3.
✗
Change line 4 to: for (int i = 0; i <= arr.length-1; i++)
Why it's wrong here
Valid but unnecessarily complex; i<arr.length is simpler.
✗
Change line 5 to: System.out.println(arr[i-1]);
Why it's wrong here
Would print wrong elements and still go out of bounds for i=3? Actually i<=3, i=3: arr[2] okay, but i=3 still accesses arr[2]? No, i=3 arr[2] works but loop still goes to i=3? Wait line 4 condition i<=arr.length, with arr.length=3, i runs 0,1,2,3. i=3: arr[3] out of bounds. Changing to arr[i-1] would cause i=0 arr[-1] exception earlier. So not valid.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the loop condition i <= arr.length with i < arr.length, not realizing that the former accesses an index one past the array's last element, causing an ArrayIndexOutOfBoundsException.
Detailed technical explanation
How to think about this question
In Java, arrays are zero-indexed, so the last valid index is arr.length - 1. The loop condition i < arr.length is the standard idiom for safe iteration. Under the hood, the JVM checks array bounds at runtime, throwing ArrayIndexOutOfBoundsException if an invalid index is accessed. In real-world scenarios, off-by-one errors are common when processing collections or reading data, and using the enhanced for-each loop (for (int x : arr)) can avoid this issue entirely.
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 1Z0-829 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.
Controlling Program Flow — This question tests Controlling Program Flow — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change line 4 to: for (int i = 0; i < arr.length; i++) — Option A is correct because it changes the loop to start at index 0 and continue while i < arr.length, which correctly iterates over all valid indices (0 to arr.length-1). The original code likely used i <= arr.length, causing an ArrayIndexOutOfBoundsException when accessing arr[i] at i = arr.length. By using i < arr.length, the loop stops before reaching the out-of-bounds index.
What should I do if I get this 1Z0-829 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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Question Discussion
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