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Oracle Java SE 1z0-830

1z0-830

Exam Code: 1z0-830

Exam Name: Java SE 21 Developer Professional

Updated Time: Oct 10, 2026

Q & A: 85 Questions and Answers

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Oracle 1z0-830 Exam Syllabus Topics:

SectionWeightObjectives
Topic 1: Concurrency and Multithreading10%- Synchronization, locks, concurrent collections, thread safety
- Thread lifecycle, Runnable, Callable, ExecutorService, virtual threads
Topic 2: Modules and Packaging5%- Create and use JAR files, modular and non-modular builds
- Module system: module-info.java, exports, requires, provides, uses
Topic 3: Using Object-Oriented Concepts20%- Overloading, overriding, Object class methods, immutable objects
- Inheritance, abstract classes, sealed classes, interfaces, polymorphism
- Enums, nested classes, local variable type inference
- Classes, records, objects, constructors, initializers, methods, fields, encapsulation
Topic 4: Working with Arrays and Collections12%- Collections Framework: List, Set, Map, Deque, Queue, sorting, searching
- Declare, instantiate, initialize, use arrays and multidimensional arrays
Topic 5: Handling Date, Time, Text, Numeric and Boolean Values12%- Use Date-Time API: LocalDate, LocalTime, LocalDateTime, Period, Duration, Instant, ZonedDateTime
- Manipulate text, text blocks, String, StringBuilder and StringBuffer
- Use primitives and wrapper classes, evaluate expressions and apply type conversions
Topic 6: Java I/O and Localization5%- Resource bundles, locale, formatting messages, numbers, dates
- File I/O, NIO.2, streams, readers/writers, serialization
Topic 7: Functional Programming and Streams15%- Optional class, primitive streams
- Lambda expressions, functional interfaces, method references
- Stream API: create, intermediate/terminal operations, parallel streams, grouping, partitioning
Topic 8: Handling Exceptions8%- Exception hierarchy, try-catch-finally, multi-catch, try-with-resources
- Create and use custom exceptions, throw, throws
Topic 9: Advanced Features and Annotations3%- Annotations, built-in annotations, custom annotations
- Generics, type parameters, wildcards, type erasure
Topic 10: Controlling Program Flow10%- Decision constructs: if-else, switch expressions and statements, pattern matching
- Loops: for, enhanced for, while, do-while, break, continue, return

Oracle Java SE 21 Developer Professional Sample Questions:

Question #1
Given:
java
List<Long> cannesFestivalfeatureFilms = LongStream.range(1, 1945)
.boxed()
.toList();
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
cannesFestivalfeatureFilms.stream()
.limit(25)
.forEach(film -> executor.submit(() -> {
System.out.println(film);
}));
}
What is printed?

A. Numbers from 1 to 1945 randomly
B. Numbers from 1 to 25 randomly
C. Numbers from 1 to 25 sequentially
D. Compilation fails
E. An exception is thrown at runtime


Question #2
Which of the following isn't a valid option of the jdeps command?

A. --print-module-deps
B. --generate-module-info
C. --list-deps
D. --list-reduced-deps
E. --check-deps
F. --generate-open-module


Question #3
Given:
java
public static void main(String[] args) {
try {
throw new IOException();
} catch (IOException e) {
throw new RuntimeException();
} finally {
throw new ArithmeticException();
}
}
What is the output?

A. ArithmeticException
B. IOException
C. Compilation fails
D. RuntimeException


Question #4
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. {2=Crazy Horse, 3=Paradis Latin, 4=Le Lido}
C. {}
D. Compilation fails.
E. An exception is thrown at runtime.


Question #5
Given:
java
interface Calculable {
long calculate(int i);
}
public class Test {
public static void main(String[] args) {
Calculable c1 = i -> i + 1; // Line 1
Calculable c2 = i -> Long.valueOf(i); // Line 2
Calculable c3 = i -> { throw new ArithmeticException(); }; // Line 3
}
}
Which lines fail to compile?

A. Line 1 and line 3
B. Line 3 only
C. Line 1 and line 2
D. Line 1 only
E. The program successfully compiles
F. Line 2 only
G. Line 2 and line 3


Solutions:

Question #1
Correct Answer: B
Question #2
Correct Answer: E
Question #3
Correct Answer: A
Question #4
Correct Answer: B
Question #5
Correct Answer: E

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