Quick Answer
The answer is 99. This output occurs because of array reference assignment aliasing in Java: when you assign one array variable to another with `a = b;`, both variables now point to the exact same array object in memory, so any modification through either reference—like setting `b[0] = 99`—is immediately visible through the other. On the Oracle Java Foundations 1Z0-811 exam, this concept tests your understanding that arrays are objects, and assignment copies the reference, not the data. The common trap is assuming `a = b;` creates a separate copy, when in fact it creates an alias—a second name for the same underlying array. Remember the memory tip: "Assigning arrays? You're just sharing the address, not the apartment."
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.
Given the code:
int[] a = {1, 2, 3}; int[] b = {4, 5}; a = b; b[0] = 99; System.out.println(a[0]);
What is the output?
3
Why wrong: 3 is from the original array a, but a no longer references that array.
1
Why wrong: 1 was the value before reassignment, but a now references the array b.
99
After the assignment a = b, both references point to the same array; changing b[0] to 99 changes the shared array, so a[0] is 99.
4
Why wrong: 4 was the original b[0] before it was changed to 99.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
99
After `a = b;`, both `a` and `b` reference the same array object. Modifying `b[0]` to 99 also changes `a[0]` because they share the same underlying array. Therefore, `a[0]` prints 99.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
3
Why it's wrong here
3 is from the original array a, but a no longer references that array.
1
Why it's wrong here
1 was the value before reassignment, but a now references the array b.
99
Why this is correct
After the assignment a = b, both references point to the same array; changing b[0] to 99 changes the shared array, so a[0] is 99.
Related concept
Read the scenario before looking for a memorised answer.
4
Why it's wrong here
4 was the original b[0] before it was changed to 99.
Common exam traps
The trap here is that candidates mistakenly think `a = b` copies the array values, leading them to believe `a[0]` retains its original value of 1 or that the arrays remain independent.
Detailed technical explanation
In Java, array variables are reference types. The assignment `a = b` copies the reference, not the array contents. This means both variables point to the same heap object, so mutations through one reference are visible through the other. This aliasing behavior is fundamental to understanding object references in Java and is a common source of confusion for beginners.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Arrays and Methods — This question tests Arrays and Methods — Read the scenario before looking for a memorised answer..
The correct answer is: 99 — After `a = b;`, both `a` and `b` reference the same array object. Modifying `b[0]` to 99 also changes `a[0]` because they share the same underlying array. Therefore, `a[0]` prints 99.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This 1Z0-811 practice question is part of Courseiva's free Oracle certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 1Z0-811 exam.
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