Java 17 1Z0-829 Sample Questions with Explanations

These original sample questions are designed to help you check how the exam topics appear in decision-style prompts. They are not taken from the live exam.

Use these sample questions as a guided self-assessment for Oracle Java SE 17 Developer (1Z0-829) topics such as overload resolution, sealed classes, records, streams, modules, collections, exceptions, and exact code-reading behavior. The prompts are deliberately compact: the hard part is deciding whether the code compiles, which rule applies first, and what the runtime contract actually says.

Where these questions fit in the 1Z0-829 guide

The sample set below is part of the Oracle Java 1Z0-829 guide path:

• Oracle certification hub
• Oracle Java guides
• 1Z0-829 exam guide
• 1Z0-829 cheat sheet
• 1Z0-829 study plan
• 1Z0-829 FAQ
• 1Z0-829 resources
• 1Z0-829 glossary

1Z0-829 Java code-reading sample questions

Work through each prompt before opening the explanation. For Java professional questions, decide whether the code compiles before predicting output.

Question 1

Topic: Overload resolution with null

What is the result of compiling and running this code?

1static void print(Object value) {
2    System.out.print("object");
3}
4static void print(String value) {
5    System.out.print("string");
6}
7public static void main(String[] args) {
8    print(null);
9}

• A. It prints object.
• B. It does not compile because null has no type.
• C. It prints string.
• D. It compiles but throws NullPointerException.

Best answer: C

Explanation: Both overloads are applicable for null, but String is more specific than Object, so the String overload is selected.

Why the other choices are weaker:

• A ignores the most-specific overload rule.
• B is wrong because null can be passed to reference-typed parameters.
• D predicts a runtime failure, but the selected method only prints text.

What this tests: Overload resolution, reference typing, and the compile-first habit.

Related topics: Overloading; Null; Method resolution; Compilation

Question 2

Topic: Sealed hierarchy legality

Which statement about this code is correct?

1sealed interface Device permits Phone, Tablet {}
2final class Phone implements Device {}
3class Tablet implements Device {}

• A. The code compiles because Tablet is listed in the permits clause.
• B. The code does not compile because sealed interfaces cannot permit classes.
• C. The code does not compile because Tablet must be declared final, sealed, or non-sealed.
• D. The code compiles only if Device is changed to an abstract class.

Best answer: C

Explanation: A direct subtype of a sealed type must explicitly choose how the hierarchy continues: final, sealed, or non-sealed. Listing Tablet in permits is necessary, but not sufficient.

Why the other choices are weaker:

• A misses the modifier requirement on permitted subclasses.
• B is false; classes can implement sealed interfaces.
• D changes the design unnecessarily and does not address the actual rule.

What this tests: Sealed type declarations and permitted-subtype obligations.

Related topics: Sealed types; Interfaces; Inheritance; Modifiers

Question 3

Topic: Optional and eager fallback work

What is printed by this code?

1static String fallback() {
2    System.out.print("fallback ");
3    return "guest";
4}
5public static void main(String[] args) {
6    var name = java.util.Optional.of("admin").orElse(fallback());
7    System.out.print(name);
8}

• A. admin
• B. fallback guest
• C. The code does not compile because orElse cannot call a method.
• D. fallback admin

Best answer: D

Explanation: The argument to orElse is evaluated before the method call, even when the Optional contains a value. The fallback method prints first, but orElse returns the contained "admin".

Why the other choices are weaker:

• A confuses orElse with lazy fallback behavior.
• B assumes the fallback return value replaces the present value.
• C invents a restriction; method calls are valid expressions.

What this tests: Optional fallback evaluation and side-effect ordering.

Related topics: Optional; Evaluation order; Method calls; Runtime output

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