- Exam Code: 1z1-830
- Exam Name: Java SE 21 Developer Professional
- Updated: Sep 13, 2026
- Q & A: 85 Questions and Answers
Oracle 1z1-830 Exam : Java SE 21 Developer Professional
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Oracle 1z1-830 Exam Syllabus Topics:
| Section | Objectives |
|---|---|
| Annotations and JDBC | - Connect to databases using JDBC - Use built-in and custom annotations - Execute SQL operations and process results |
| Functional Programming | - Work with functional interfaces - Process data using Stream API - Use lambda expressions and method references |
| Handling Date, Time, Text, Numeric and Boolean Values | - Work with primitive wrappers and number formatting - Use date, time, duration, period, and localization APIs - Use String, StringBuilder, and related APIs |
| Object-Oriented Programming | - Create and use classes, interfaces, enums, and records - Apply inheritance and polymorphism - Implement encapsulation and abstraction |
| Java Concurrency | - Create and manage threads - Work with concurrent collections and executors - Use virtual threads |
| Modules and Packaging | - Package and deploy applications - Manage dependencies and exports - Create and use Java modules |
| Controlling Program Flow | - Apply decision statements and loops - Use switch expressions and pattern matching - Work with records and sealed classes |
| Exception Handling | - Use try-with-resources - Handle checked and unchecked exceptions - Create custom exceptions |
| Collections and Generics | - Use sequenced collections and maps - Use List, Set, Map, Queue, and Deque implementations - Apply generics and bounded types |
| Java I/O and NIO | - Read and write files - Process file system resources - Use Path, Files, and related APIs |
Oracle Java SE 21 Developer Professional Sample Questions:
Question #1
Which of the following statements oflocal variables declared with varareinvalid?(Choose 4)
- A. var e;
- B. var b = 2, c = 3.0;
- C. var h = (g = 7);
- D. var f = { 6 };
- E. var d[] = new int[4];
- F. var a = 1;(Valid: var correctly infers int)
Correct Answer: A,B,D,E 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #2
Given:
java
public class OuterClass {
String outerField = "Outer field";
class InnerClass {
void accessMembers() {
System.out.println(outerField);
}
}
public static void main(String[] args) {
System.out.println("Inner class:");
System.out.println("------------");
OuterClass outerObject = new OuterClass();
InnerClass innerObject = new InnerClass(); // n1
innerObject.accessMembers(); // n2
}
}
What is printed?
- A. Compilation fails at line n2.
- B. An exception is thrown at runtime.
- C. Compilation fails at line n1.
- D. markdown
Inner class:
------------
Outer field - E. Nothing
Correct Answer: C 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #3
Given:
java
List<String> frenchAuthors = new ArrayList<>();
frenchAuthors.add("Victor Hugo");
frenchAuthors.add("Gustave Flaubert");
Which compiles?
- A. Map<String, List<String>> authorsMap4 = new HashMap<String, ArrayList<String>>(); java authorsMap4.put("FR", frenchAuthors);
- B. var authorsMap3 = new HashMap<>();
java
authorsMap3.put("FR", frenchAuthors); - C. Map<String, ? extends List<String>> authorsMap2 = new HashMap<String, ArrayList<String>> (); java authorsMap2.put("FR", frenchAuthors);
- D. Map<String, List<String>> authorsMap5 = new HashMap<String, List<String>>(); java authorsMap5.put("FR", frenchAuthors);
- E. Map<String, ArrayList<String>> authorsMap1 = new HashMap<>();
java
authorsMap1.put("FR", frenchAuthors);
Correct Answer: A,B,D 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #4
Given:
java
DoubleStream doubleStream = DoubleStream.of(3.3, 4, 5.25, 6.66);
Predicate<Double> doublePredicate = d -> d < 5;
System.out.println(doubleStream.anyMatch(doublePredicate));
What is printed?
- A. false
- B. An exception is thrown at runtime
- C. 3.3
- D. Compilation fails
- E. true
Correct Answer: D 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
Question #5
Given:
java
String textBlock = """
j \
a \t
v \s
a \
""";
System.out.println(textBlock.length());
What is the output?
- A. 10
- B. 14
- C. 11
- D. 12
Correct Answer: D 🗳️
Explanation: Only visible for Exam4Tests members. You can sign-up / login (it's free).
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