Oracle 1z1-830 : Java SE 21 Developer Professional
- Exam Code: 1z1-830
- Exam Name: Java SE 21 Developer Professional
- Updated: Oct 08, 2026
- Q & A: 85 Questions and Answers
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Oracle 1z1-830 Exam Syllabus Topics:
| Section | Objectives |
|---|---|
| Topic 1: Concurrency and Multithreading | - Thread management
|
| Topic 2: Database Connectivity (JDBC) | - Database interaction
|
| Topic 3: Object-Oriented Programming | - Core OOP principles
|
| Topic 4: Advanced Java Features (Java SE 21) | - Modern language features
|
| Topic 5: Java Language Fundamentals | - Java syntax and language structure
|
| Topic 6: Core APIs | - Java standard library usage
|
| Topic 7: Input/Output and File Handling | - NIO and file operations
|
| Topic 8: Exception Handling and Debugging | - Error handling mechanisms
|
Oracle Java SE 21 Developer Professional Sample Questions:
Given:
java
Map<String, Integer> map = Map.of("b", 1, "a", 3, "c", 2);
TreeMap<String, Integer> treeMap = new TreeMap<>(map);
System.out.println(treeMap);
What is the output of the given code fragment?
- A. {a=3, b=1, c=2}
- B. {a=1, b=2, c=3}
- C. {c=2, a=3, b=1}
- D. {c=1, b=2, a=3}
- E. Compilation fails
- F. {b=1, c=2, a=3}
- G. {b=1, a=3, c=2}
Correct Answer: A 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
Given:
java
var _ = 3;
var $ = 7;
System.out.println(_ + $);
What is printed?
- A. 10
- B. Compilation fails.
- C. _$
- D. It throws an exception.
Correct Answer: B 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
Given:
var cabarets = new TreeMap<>();
cabarets.put(1, "Moulin Rouge");
cabarets.put(2, "Crazy Horse");
cabarets.put(3, "Paradis Latin");
cabarets.put(4, "Le Lido");
cabarets.put(5, "Folies Bergere");
System.out.println(cabarets.subMap(2, true, 5, false));
What is printed?
- A. CopyEdit{2=Crazy Horse, 3=Paradis Latin, 4=Le Lido, 5=Folies Bergere}
- B. An exception is thrown at runtime.
- C. Compilation fails.
- D. {}
- E. {2=Crazy Horse, 3=Paradis Latin, 4=Le Lido}
Correct Answer: E 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
Given:
java
void verifyNotNull(Object input) {
boolean enabled = false;
assert enabled = true;
assert enabled;
System.out.println(input.toString());
assert input != null;
}
When does the given method throw a NullPointerException?
- A. Only if assertions are disabled and the input argument is null
- B. Only if assertions are enabled and the input argument isn't null
- C. Only if assertions are enabled and the input argument is null
- D. Only if assertions are disabled and the input argument isn't null
- E. A NullPointerException is never thrown
Correct Answer: A 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
How would you create a ConcurrentHashMap configured to allow a maximum of 10 concurrent writer threads and an initial capacity of 42?
Which of the following options meets this requirement?
- A. var concurrentHashMap = new ConcurrentHashMap();
- B. var concurrentHashMap = new ConcurrentHashMap(42, 10);
- C. var concurrentHashMap = new ConcurrentHashMap(42);
- D. None of the suggestions.
- E. var concurrentHashMap = new ConcurrentHashMap(42, 0.88f, 10);
Correct Answer: E 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
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