The answer is a compilation failure due to type mismatch. This occurs because the variable `num` is declared as `final`, which means it can be assigned a value exactly once, and any subsequent attempt to reassign it—such as `num = 5;` inside a switch case—directly violates the final variable constraint. The compiler detects this illegal reassignment and reports a type mismatch error, since the assignment is incompatible with the final modifier. On the Oracle Java Foundations 1Z0-811 exam, this question tests your understanding of the interaction between `final` variables and control flow statements like `switch`; a common trap is assuming that a `final` variable can be reassigned within a switch block because each case appears to be a separate scope. Remember the memory tip: "Final is forever—once set, you cannot reset."
1Z0-811 Java Basics and Syntax Practice Question
This 1Z0-811 practice question tests your understanding of java basics and syntax. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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
public class MyClass {
public static void main(String[] args) {
int num = 10;
if(num = 5) {
System.out.println("Five");
}
}
}
Refer to the exhibit. What happens when you compile this code?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Compilation fails because of type mismatch
The code fails to compile because the variable `num` is declared as `final`, meaning its value cannot be changed after initialization. The switch statement attempts to assign a new value to `num` in each case label (e.g., `case 1: num = 5;`), which violates the final variable constraint, causing a compilation error due to type mismatch (the assignment is incompatible with the final modifier).
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.
✓
Compilation fails because of type mismatch
Why this is correct
Correct. Assignment returns int, not boolean.
Related concept
Read the scenario before looking for a memorised answer.
✗
Compilation fails because num is final
Why it's wrong here
Incorrect. num is not declared final.
✗
Prints "Five"
Why it's wrong here
Incorrect. Code does not compile.
✗
Prints nothing
Why it's wrong here
Incorrect. Code does not compile.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Oracle often tests the distinction between using a final variable in a switch expression (allowed) versus attempting to reassign it inside the switch body (not allowed), leading candidates to incorrectly assume that final variables can be modified in any context.
Detailed technical explanation
How to think about this question
In Java, a `final` variable can be used in a switch expression or as a case label value, but it cannot be reassigned within the switch body. The compiler enforces this at compile time by checking that any assignment to a final variable is illegal, regardless of the switch control flow. This is a common source of errors when developers mistakenly treat final variables as mutable within conditional blocks.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Java Basics and Syntax — This question tests Java Basics and Syntax — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Compilation fails because of type mismatch — The code fails to compile because the variable `num` is declared as `final`, meaning its value cannot be changed after initialization. The switch statement attempts to assign a new value to `num` in each case label (e.g., `case 1: num = 5;`), which violates the final variable constraint, causing a compilation error due to type mismatch (the assignment is incompatible with the final modifier).
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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Question Discussion
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