- Exam Code: 1z0-830
- Exam Name: Java SE 21 Developer Professional
- Updated: Oct 31, 2026
- Q & A: 85 Questions and Answers
Oracle 1z0-830 Exam : Java SE 21 Developer Professional
PDF Version DemoAbout Oracle 1z0-830 Exam
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Oracle 1z0-830 Exam Syllabus Topics:
| Section | Objectives |
|---|---|
| Topic 1: Java I/O and NIO | - Read and write files - Process file system resources - Use Path, Files, and related APIs |
| Topic 2: Modules and Packaging | - Manage dependencies and exports - Create and use Java modules - Package and deploy applications |
| Topic 3: Java Concurrency | - Work with concurrent collections and executors - Create and manage threads - Use virtual threads |
| Topic 4: Handling Date, Time, Text, Numeric and Boolean Values | - Use String, StringBuilder, and related APIs - Work with primitive wrappers and number formatting - Use date, time, duration, period, and localization APIs |
| Topic 5: Controlling Program Flow | - Apply decision statements and loops - Work with records and sealed classes - Use switch expressions and pattern matching |
| Topic 6: Object-Oriented Programming | - Implement encapsulation and abstraction - Apply inheritance and polymorphism - Create and use classes, interfaces, enums, and records |
| Topic 7: Exception Handling | - Create custom exceptions - Use try-with-resources - Handle checked and unchecked exceptions |
| Topic 8: Annotations and JDBC | - Execute SQL operations and process results - Connect to databases using JDBC - Use built-in and custom annotations |
| Topic 9: Collections and Generics | - Use sequenced collections and maps - Use List, Set, Map, Queue, and Deque implementations - Apply generics and bounded types |
| Topic 10: Functional Programming | - Work with functional interfaces - Use lambda expressions and method references - Process data using Stream API |
Oracle Java SE 21 Developer Professional Sample Questions:
Question #1
What do the following print?
java
public class DefaultAndStaticMethods {
public static void main(String[] args) {
WithStaticMethod.print();
}
}
interface WithDefaultMethod {
default void print() {
System.out.print("default");
}
}
interface WithStaticMethod extends WithDefaultMethod {
static void print() {
System.out.print("static");
}
}
- A. nothing
- B. static
- C. Compilation fails
- D. default
Correct Answer: B 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #2
Given:
java
var counter = 0;
do {
System.out.print(counter + " ");
} while (++counter < 3);
What is printed?
- A. 1 2 3 4
- B. 0 1 2 3
- C. 1 2 3
- D. An exception is thrown.
- E. Compilation fails.
- F. 0 1 2
Correct Answer: F 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #3
Given:
java
List<String> l1 = new ArrayList<>(List.of("a", "b"));
List<String> l2 = new ArrayList<>(Collections.singletonList("c"));
Collections.copy(l1, l2);
l2.set(0, "d");
System.out.println(l1);
What is the output of the given code fragment?
- A. An IndexOutOfBoundsException is thrown
- B. [c, b]
- C. [a, b]
- D. [d, b]
- E. [d]
- F. An UnsupportedOperationException is thrown
Correct Answer: B 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #4
Given:
java
package com.vv;
import java.time.LocalDate;
public class FetchService {
public static void main(String[] args) throws Exception {
FetchService service = new FetchService();
String ack = service.fetch();
LocalDate date = service.fetch();
System.out.println(ack + " the " + date.toString());
}
public String fetch() {
return "ok";
}
public LocalDate fetch() {
return LocalDate.now();
}
}
What will be the output?
- A. ok the 2024-07-10T07:17:45.523939600
- B. An exception is thrown
- C. ok the 2024-07-10
- D. Compilation fails
Correct Answer: D 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #5
Given:
java
Optional o1 = Optional.empty();
Optional o2 = Optional.of(1);
Optional o3 = Stream.of(o1, o2)
.filter(Optional::isPresent)
.findAny()
.flatMap(o -> o);
System.out.println(o3.orElse(2));
What is the given code fragment's output?
- A. 2
- B. Optional[1]
- C. 0
- D. An exception is thrown
- E. Optional.empty
- F. 1
- G. Compilation fails
Correct Answer: F 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
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