Free Oracle 1z0-830 Practice Test & Real Exam Questions

Exam Code/Number: 1z0-830
Exam Name/Title: Java SE 21 Developer Professional
Certification Provider: Oracle
Corresponding Certification: Java SE

Exam Questions: 85
Updated On: Jun 18, 2026

Question #10

Which of the following suggestions compile?(Choose two.)

A. java
public sealed class Figure
permits Circle, Rectangle {}
final sealed class Circle extends Figure {
float radius;
}
non-sealed class Rectangle extends Figure {
float length, width;
}

B. java
sealed class Figure permits Rectangle {}
final class Rectangle extends Figure {
float length, width;
}

C. java
sealed class Figure permits Rectangle {}
public class Rectangle extends Figure {
float length, width;
}

D. java
public sealed class Figure
permits Circle, Rectangle {}
final class Circle extends Figure {
float radius;
}
non-sealed class Rectangle extends Figure {
float length, width;
}

Discussion 0

Correct Answer: B,D Vote an answer

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Question #11

Which of the following java.io.Console methods doesnotexist?

A. readLine()

B. reader()

C. readPassword(String fmt, Object... args)

D. readPassword()

E. read()

F. readLine(String fmt, Object... args)

Discussion 0

Correct Answer: E Vote an answer

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Question #12

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

A. Everything compiles

B. SmartPhone interface does not compile

C. Iphone15 class does not compile

D. An exception is thrown at running Iphone15.ring();

Discussion 0

Correct Answer: C Vote an answer

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Question #13

Which two of the following aren't the correct ways to create a Stream?

A. Stream stream = Stream.of();

B. Stream<String> stream = Stream.builder().add("a").build();

C. Stream stream = Stream.ofNullable("a");

D. Stream stream = new Stream();

E. Stream stream = Stream.empty();

F. Stream stream = Stream.generate(() -> "a");

Discussion 0

Correct Answer: B,D Vote an answer

Question #14

Which of the followingisn'ta correct way to write a string to a file?

A. java
try (BufferedWriter writer = new BufferedWriter("file.txt")) {
writer.write("Hello");
}

B. java
try (FileWriter writer = new FileWriter("file.txt")) {
writer.write("Hello");
}

C. java
Path path = Paths.get("file.txt");
byte[] strBytes = "Hello".getBytes();
Files.write(path, strBytes);

D. java
try (PrintWriter printWriter = new PrintWriter("file.txt")) {
printWriter.printf("Hello %s", "James");
}

E. java
try (FileOutputStream outputStream = new FileOutputStream("file.txt")) { byte[] strBytes = "Hello".getBytes(); outputStream.write(strBytes);
}

F. None of the suggestions

Discussion 0

Correct Answer: A Vote an answer

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Question #15

Given:
java
public static void main(String[] args) {
try {
throw new IOException();
} catch (IOException e) {
throw new RuntimeException();
} finally {
throw new ArithmeticException();
}
}
What is the output?

A. RuntimeException

B. IOException

C. Compilation fails

D. ArithmeticException

Discussion 0

Correct Answer: D Vote an answer

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Question #16

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

Discussion 0

Correct Answer: A Vote an answer

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Question #17

How would you create a ConcurrentHashMap configured to allow a maximum of 10 concurrent writer threads and an initial capacity of 42?
Which of the following options meets this requirement?

A. var concurrentHashMap = new ConcurrentHashMap(42, 10);

B. None of the suggestions.

C. var concurrentHashMap = new ConcurrentHashMap();

D. var concurrentHashMap = new ConcurrentHashMap(42, 0.88f, 10);

E. var concurrentHashMap = new ConcurrentHashMap(42);

Discussion 0

Correct Answer: D Vote an answer

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Question #18

Given:
java
double amount = 42_000.00;
NumberFormat format = NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.
SHORT);
System.out.println(format.format(amount));
What is the output?

A. 42 k

B. 42000

C. 42000E

D. 42 000,00 €

Discussion 0

Correct Answer: A Vote an answer

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