Oracle Java SE 21 Developer Professional : 1z0-830 exam

1z0-830 real exams

Exam Code: 1z0-830

Exam Name: Java SE 21 Developer Professional

Updated: Aug 15, 2026

Q & A: 85 Questions and Answers

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Oracle 1z0-830 Exam Syllabus Topics:

SectionObjectives
Database Connectivity (JDBC)- Database interaction
  • 1. JDBC API usage
    • 2. SQL execution and result handling
      Concurrency and Multithreading- Thread management
      • 1. Thread lifecycle and synchronization
        • 2. Virtual threads and structured concurrency concepts
          Java Language Fundamentals- Java syntax and language structure
          • 1. Control flow statements
            • 2. Data types, variables, and operators
              Exception Handling and Debugging- Error handling mechanisms
              • 1. Try-with-resources
                • 2. Checked vs unchecked exceptions
                  Core APIs- Java standard library usage
                  • 1. Streams and functional programming
                    • 2. Date and Time API
                      • 3. Collections Framework
                        Input/Output and File Handling- NIO and file operations
                        • 1. Serialization basics
                          • 2. File, Path, and Streams APIs
                            Object-Oriented Programming- Core OOP principles
                            • 1. Abstract classes and interfaces
                              • 2. Encapsulation, inheritance, polymorphism
                                Advanced Java Features (Java SE 21)- Modern language features
                                • 1. Records and record patterns
                                  • 2. Sealed classes
                                    • 3. Pattern matching for switch
                                      • 4. Virtual threads (Project Loom)

                                        Oracle Java SE 21 Developer Professional Sample Questions:

                                        1. Given:
                                        java
                                        LocalDate localDate = LocalDate.of(2020, 8, 8);
                                        Date date = java.sql.Date.valueOf(localDate);
                                        DateFormat formatter = new SimpleDateFormat(/* pattern */);
                                        String output = formatter.format(date);
                                        System.out.println(output);
                                        It's known that the given code prints out "August 08".
                                        Which of the following should be inserted as the pattern?

                                        A) MMM dd
                                        B) MM dd
                                        C) MMMM dd
                                        D) MM d


                                        2. What does the following code print?
                                        java
                                        import java.util.stream.Stream;
                                        public class StreamReduce {
                                        public static void main(String[] args) {
                                        Stream<String> stream = Stream.of("J", "a", "v", "a");
                                        System.out.print(stream.reduce(String::concat));
                                        }
                                        }

                                        A) Optional[Java]
                                        B) Compilation fails
                                        C) null
                                        D) Java


                                        3. 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) 666 666
                                        B) Compilation fails
                                        C) 42 42
                                        D) 666 42


                                        4. 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 followed by an exception
                                        D) Compilation fails.
                                        E) bim bam boom


                                        5. Given:
                                        java
                                        interface SmartPhone {
                                        boolean ring();
                                        }
                                        class Iphone15 implements SmartPhone {
                                        boolean isRinging;
                                        boolean ring() {
                                        isRinging = !isRinging;
                                        return isRinging;
                                        }
                                        }
                                        Choose the right statement.

                                        A) SmartPhone interface does not compile
                                        B) An exception is thrown at running Iphone15.ring();
                                        C) Iphone15 class does not compile
                                        D) Everything compiles


                                        Solutions:

                                        Question # 1
                                        Answer: C
                                        Question # 2
                                        Answer: A
                                        Question # 3
                                        Answer: C
                                        Question # 4
                                        Answer: E
                                        Question # 5
                                        Answer: C

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