Java SE 21 Developer Professional: 1z1-830 Exam

"Java SE 21 Developer Professional", also known as 1z1-830 exam, is a Oracle Certification. With the complete collection of questions and answers, Pass4sureCert has assembled to take you through 85 Q&As to your 1z1-830 Exam preparation. In the 1z1-830 exam resources, you will cover every field and category in Java SE Certification helping to ready you for your successful Oracle Certification.

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  • Exam Code: 1z1-830
  • Exam Name: Java SE 21 Developer Professional
  • Certification Provider: Oracle
  • Corresponding Certification: Java SE
  • Updated: Sep 14, 2026
  • No. of Questions: 85 Questions & Answers with Testing Engine
  • Download Limit: Unlimited

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Oracle 1z1-830 Exam Syllabus Topics:

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

Oracle Java SE 21 Developer Professional Sample Questions:

Given:
java
public class BoomBoom implements AutoCloseable {
public static void main(String[] args) {
try (BoomBoom boomBoom = new BoomBoom()) {
System.out.print("bim ");
throw new Exception();
} catch (Exception e) {
System.out.print("boom ");
}
}
@Override
public void close() throws Exception {
System.out.print("bam ");
throw new RuntimeException();
}
}
What is printed?

  • A. bim boom bam
  • B. bim boom
  • C. bim bam boom
  • D. bim bam followed by an exception
  • E. Compilation fails.
Reveal Solution  Discussion  0

Correct Answer: C  🗳️

Explanation: Only visible for Pass4sureCert members. You can sign-up / login (it's free).

Given:
java
DoubleSummaryStatistics stats1 = new DoubleSummaryStatistics();
stats1.accept(4.5);
stats1.accept(6.0);
DoubleSummaryStatistics stats2 = new DoubleSummaryStatistics();
stats2.accept(3.0);
stats2.accept(8.5);
stats1.combine(stats2);
System.out.println("Sum: " + stats1.getSum() + ", Max: " + stats1.getMax() + ", Avg: " + stats1.getAverage()); What is printed?

  • A. An exception is thrown at runtime.
  • B. Compilation fails.
  • C. Sum: 22.0, Max: 8.5, Avg: 5.0
  • D. Sum: 22.0, Max: 8.5, Avg: 5.5
Reveal Solution  Discussion  0

Correct Answer: D  🗳️

Explanation: Only visible for Pass4sureCert members. You can sign-up / login (it's free).

Given:
java
Integer frenchRevolution = 1789;
Object o1 = new String("1789");
Object o2 = frenchRevolution;
frenchRevolution = null;
Object o3 = o2.toString();
System.out.println(o1.equals(o3));
What is printed?

  • A. false
  • B. Compilation fails.
  • C. true
  • D. A NullPointerException is thrown.
  • E. A ClassCastException is thrown.
Reveal Solution  Discussion  0

Correct Answer: C  🗳️

Explanation: Only visible for Pass4sureCert members. You can sign-up / login (it's free).

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 UnsupportedOperationException is thrown
  • B. [a, b]
  • C. [d, b]
  • D. An IndexOutOfBoundsException is thrown
  • E. [c, b]
  • F. [d]
Reveal Solution  Discussion  0

Correct Answer: E  🗳️

Explanation: Only visible for Pass4sureCert members. You can sign-up / login (it's free).

Which of the following doesnotexist?

  • A. Supplier<T>
  • B. BiSupplier<T, U, R>
  • C. They all exist.
  • D. BooleanSupplier
  • E. LongSupplier
  • F. DoubleSupplier
Reveal Solution  Discussion  0

Correct Answer: B  🗳️

Explanation: Only visible for Pass4sureCert members. You can sign-up / login (it's free).

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