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

  • Exam Code: 1z0-830
  • Exam Name: Java SE 21 Developer Professional
  • Updated: Aug 19, 2026
  • Q & A: 85 Questions and Answers

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About Oracle Java SE 21 Developer Professional : 1z0-830 Exam Questions

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Oracle 1z0-830 Exam Syllabus Topics:

SectionObjectives
Topic 1: Java Language Fundamentals- Java syntax and language structure
  • 1. Control flow statements
    • 2. Data types, variables, and operators
      Topic 2: Concurrency and Multithreading- Thread management
      • 1. Thread lifecycle and synchronization
        • 2. Virtual threads and structured concurrency concepts
          Topic 3: Exception Handling and Debugging- Error handling mechanisms
          • 1. Checked vs unchecked exceptions
            • 2. Try-with-resources
              Topic 4: Advanced Java Features (Java SE 21)- Modern language features
              • 1. Records and record patterns
                • 2. Pattern matching for switch
                  • 3. Sealed classes
                    • 4. Virtual threads (Project Loom)
                      Topic 5: Object-Oriented Programming- Core OOP principles
                      • 1. Encapsulation, inheritance, polymorphism
                        • 2. Abstract classes and interfaces
                          Topic 6: Core APIs- Java standard library usage
                          • 1. Date and Time API
                            • 2. Collections Framework
                              • 3. Streams and functional programming
                                Topic 7: Input/Output and File Handling- NIO and file operations
                                • 1. Serialization basics
                                  • 2. File, Path, and Streams APIs
                                    Topic 8: Database Connectivity (JDBC)- Database interaction
                                    • 1. JDBC API usage
                                      • 2. SQL execution and result handling

                                        Oracle Java SE 21 Developer Professional Sample Questions:

                                        1. Given:
                                        java
                                        StringBuffer us = new StringBuffer("US");
                                        StringBuffer uk = new StringBuffer("UK");
                                        Stream<StringBuffer> stream = Stream.of(us, uk);
                                        String output = stream.collect(Collectors.joining("-", "=", ""));
                                        System.out.println(output);
                                        What is the given code fragment's output?

                                        A) =US-UK
                                        B) US=UK
                                        C) An exception is thrown.
                                        D) US-UK
                                        E) Compilation fails.
                                        F) -US=UK


                                        2. Given:
                                        java
                                        System.out.print(Boolean.logicalAnd(1 == 1, 2 < 1));
                                        System.out.print(Boolean.logicalOr(1 == 1, 2 < 1));
                                        System.out.print(Boolean.logicalXor(1 == 1, 2 < 1));
                                        What is printed?

                                        A) falsetruetrue
                                        B) truetruefalse
                                        C) truetruetrue
                                        D) truefalsetrue
                                        E) Compilation fails


                                        3. Given:
                                        java
                                        var ceo = new HashMap<>();
                                        ceo.put("Sundar Pichai", "Google");
                                        ceo.put("Tim Cook", "Apple");
                                        ceo.put("Mark Zuckerberg", "Meta");
                                        ceo.put("Andy Jassy", "Amazon");
                                        Does the code compile?

                                        A) False
                                        B) True


                                        4. Given:
                                        java
                                        Period p = Period.between(
                                        LocalDate.of(2023, Month.MAY, 4),
                                        LocalDate.of(2024, Month.MAY, 4));
                                        System.out.println(p);
                                        Duration d = Duration.between(
                                        LocalDate.of(2023, Month.MAY, 4),
                                        LocalDate.of(2024, Month.MAY, 4));
                                        System.out.println(d);
                                        What is the output?

                                        A) P1Y
                                        PT8784H
                                        B) PT8784H
                                        P1Y
                                        C) UnsupportedTemporalTypeException
                                        D) P1Y
                                        UnsupportedTemporalTypeException


                                        5. Given:
                                        java
                                        void verifyNotNull(Object input) {
                                        boolean enabled = false;
                                        assert enabled = true;
                                        assert enabled;
                                        System.out.println(input.toString());
                                        assert input != null;
                                        }
                                        When does the given method throw a NullPointerException?

                                        A) Only if assertions are disabled and the input argument is null
                                        B) Only if assertions are disabled and the input argument isn't null
                                        C) Only if assertions are enabled and the input argument isn't null
                                        D) Only if assertions are enabled and the input argument is null
                                        E) A NullPointerException is never thrown


                                        Solutions:

                                        Question # 1
                                        Answer: A
                                        Question # 2
                                        Answer: D
                                        Question # 3
                                        Answer: A
                                        Question # 4
                                        Answer: D
                                        Question # 5
                                        Answer: A

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