Oracle 1z0-830 : Java SE 21 Developer Professional
- Exam Code: 1z0-830
- Exam Name: Java SE 21 Developer Professional
- Updated: Oct 07, 2026
- Q & A: 85 Questions and Answers
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Oracle 1z0-830 Exam Syllabus Topics:
| Section | Weight | Objectives |
|---|---|---|
| Topic 1: Functional Programming and Streams | 15% | - Lambda expressions, functional interfaces, method references - Stream API: create, intermediate/terminal operations, parallel streams, grouping, partitioning - Optional class, primitive streams |
| Topic 2: Advanced Features and Annotations | 3% | - Annotations, built-in annotations, custom annotations - Generics, type parameters, wildcards, type erasure |
| Topic 3: Working with Arrays and Collections | 12% | - Collections Framework: List, Set, Map, Deque, Queue, sorting, searching - Declare, instantiate, initialize, use arrays and multidimensional arrays |
| Topic 4: Java I/O and Localization | 5% | - File I/O, NIO.2, streams, readers/writers, serialization - Resource bundles, locale, formatting messages, numbers, dates |
| Topic 5: Concurrency and Multithreading | 10% | - Thread lifecycle, Runnable, Callable, ExecutorService, virtual threads - Synchronization, locks, concurrent collections, thread safety |
| Topic 6: Handling Date, Time, Text, Numeric and Boolean Values | 12% | - Use primitives and wrapper classes, evaluate expressions and apply type conversions - Use Date-Time API: LocalDate, LocalTime, LocalDateTime, Period, Duration, Instant, ZonedDateTime - Manipulate text, text blocks, String, StringBuilder and StringBuffer |
| Topic 7: Handling Exceptions | 8% | - Exception hierarchy, try-catch-finally, multi-catch, try-with-resources - Create and use custom exceptions, throw, throws |
| Topic 8: Controlling Program Flow | 10% | - Loops: for, enhanced for, while, do-while, break, continue, return - Decision constructs: if-else, switch expressions and statements, pattern matching |
| Topic 9: Modules and Packaging | 5% | - Module system: module-info.java, exports, requires, provides, uses - Create and use JAR files, modular and non-modular builds |
| Topic 10: Using Object-Oriented Concepts | 20% | - Inheritance, abstract classes, sealed classes, interfaces, polymorphism - Classes, records, objects, constructors, initializers, methods, fields, encapsulation - Overloading, overriding, Object class methods, immutable objects - Enums, nested classes, local variable type inference |
Oracle Java SE 21 Developer Professional Sample Questions:
Given:
java
var sList = new CopyOnWriteArrayList<Customer>();
Which of the following statements is correct?
- A. The CopyOnWriteArrayList class is not thread-safe and does not prevent interference amongconcurrent threads.
- B. The CopyOnWriteArrayList class's iterator reflects all additions, removals, or changes to the list since the iterator was created.
- C. Element-changing operations on iterators of CopyOnWriteArrayList, such as remove, set, and add, are supported and do not throw UnsupportedOperationException.
- D. The CopyOnWriteArrayList class is a thread-safe variant of ArrayList where all mutative operations are implemented by making a fresh copy of the underlying array.
- E. The CopyOnWriteArrayList class does not allow null elements.
Correct Answer: D 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
Given:
java
var lyrics = """
Quand il me prend dans ses bras
Qu'il me parle tout bas
Je vois la vie en rose
""";
for ( int i = 0, int j = 3; i < j; i++ ) {
System.out.println( lyrics.lines()
.toList()
.get( i ) );
}
What is printed?
- A. vbnet
Quand il me prend dans ses bras
Qu'il me parle tout bas
Je vois la vie en rose - B. An exception is thrown at runtime.
- C. Compilation fails.
- D. Nothing
Correct Answer: C 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
Given a properties file on the classpath named Person.properties with the content:
ini
name=James
And:
java
public class Person extends ListResourceBundle {
protected Object[][] getContents() {
return new Object[][]{
{"name", "Jeanne"}
};
}
}
And:
java
public class Test {
public static void main(String[] args) {
ResourceBundle bundle = ResourceBundle.getBundle("Person");
String name = bundle.getString("name");
System.out.println(name);
}
}
What is the given program's output?
- A. JamesJeanne
- B. James
- C. MissingResourceException
- D. JeanneJames
- E. Compilation fails
- F. Jeanne
Correct Answer: F 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
Given:
java
public class ExceptionPropagation {
public static void main(String[] args) {
try {
thrower();
System.out.print("Dom Perignon, ");
} catch (Exception e) {
System.out.print("Chablis, ");
} finally {
System.out.print("Saint-Emilion");
}
}
static int thrower() {
try {
int i = 0;
return i / i;
} catch (NumberFormatException e) {
System.out.print("Rose");
return -1;
} finally {
System.out.print("Beaujolais Nouveau, ");
}
}
}
What is printed?
- A. Beaujolais Nouveau, Chablis, Dom Perignon, Saint-Emilion
- B. Saint-Emilion
- C. Beaujolais Nouveau, Chablis, Saint-Emilion
- D. Rose
Correct Answer: C 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
What do the following print?
java
public class Main {
int instanceVar = staticVar;
static int staticVar = 666;
public static void main(String args[]) {
System.out.printf("%d %d", new Main().instanceVar, staticVar);
}
static {
staticVar = 42;
}
}
- A. 42 42
- B. 666 42
- C. 666 666
- D. Compilation fails
Correct Answer: A 🗳️
Explanation: Only visible for Free4Torrent members. You can sign-up / login (it's free).
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