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Guide for Java SE 21 Developer Professional

Quiz Java SE 21 Developer Professional

Free Test
/ 10

Quiz

1/10
What functionality is provided by the jdeps tool?
Select the answer
1 correct answer
A.
Creates a runtime image for a Java application.
B.
Analyzes dependencies between modules and classes.
C.
Generates documentation for Java code.
D.
Compiles Java source code into bytecode. A. C

Quiz

2/10
Given a Stream of Strings, which lambda expression correctly checks if all strings start with the letter
"A"?
Select the answer
1 correct answer
A.
java Stream<String> names = Stream.of("Alice", "Bob", "Charlie"); boolean allStartWithA = names.allMatch(n -> n.charAt(0) == 'A');
B.
java Stream<String> names = Stream.of("Alice", "Bob", "Charlie"); boolean allStartWithA = names.anyMatch(n -> n.charAt(0) == 'A'); (**Incorrect - anyMatch checks for at least one element**
C.
java Stream<String> names = Stream.of("Alice", "Bob", "Charlie"); boolean allStartWithA = names.filter(n -> n.charAt(0) == 'A').count() == names.count(); (**Incorrect - Manual filtering followed by count comparison**)
D.
```java Stream<String> names = Stream.of("Alice", "Bob", "Charlie"); boolean allStartWithA = names.noneMatch(n -> n.charAt(0) != 'A'); (Incorrect - noneMatch checks for no elements not starting with 'A') A. C

Quiz

3/10
A Path object represents which of the following?
Select the answer
1 correct answer
A.
The content of a file
B.
A byte stream associated with a file
C.
The location (name and directory structure) of a file or directory
D.
Permissions associated with a file A. D

Quiz

4/10
What interface does a class need to implement to be eligible for serialization?
Select the answer
1 correct answer
A.
Serializable
B.
Cloneable
C.
ObjectOutputStream
D.
DataOutputStream A. C

Quiz

5/10
What is the purpose of a functional interface in Java?
Select the answer
1 correct answer
A.
To define a set of static helper methods.
B.
To provide a callback mechanism for lambda expressions.
C.
To enforce specific naming conventions for methods.
D.
To restrict access to methods within an interface. A. B

Quiz

6/10
How can you add a new element "Apple" to the end of a LinkedList named fruits?
Select the answer
1 correct answer
A.
```java fruits.addFirst("Apple");
B.
```java fruits.set(fruits.size(), "Apple");
C.
```java fruits.addLast("Apple");
D.
```java fruits.append("Apple"); // This method doesn't exist in LinkedList A. A

Quiz

7/10
Which of the following statements is NOT true about the synchronized keyword in Java?
Select the answer
1 correct answer
A.
It guarantees exclusive access to a code block by a single thread at a time.
B.
It can be applied to methods and code blocks
C.
It automatically handles thread-safety for immutable objects.
D.
It can lead to deadlocks if used incorrectly. A. B

Quiz

8/10
Given a Stream of integers, which code snippet efficiently finds the maximum value using a reduction
operation?
Select the answer
1 correct answer
A.
java List<Integer> numbers = Arrays.asList(10, 5, 20); int max = numbers.stream().filter(n -> n > 15).findFirst().orElse(0); (**Incorrect - Filters then finds first**)
B.
java List<Integer> numbers = Arrays.asList(10, 5, 20); int max = numbers.stream().max(Integer::compareTo).get(); (**Incorrect - max with Comparator, not efficient for reduction**
C.
java List<Integer> numbers = Arrays.asList(10, 5, 20); int max = numbers.stream().reduce(Integer.MIN_VALUE, (a, b) -> Math.max(a, b)); (**Incorrect - Initial value and custom reduction function**)
D.
```java List<Integer> numbers = Arrays.asList(10, 5, 20); int max = numbers.stream().max(Integer::compareTo).orElse(0); A. C

Quiz

9/10
Which of the following statements is true about interfaces in Java?
Select the answer
1 correct answer
A.
Interfaces can directly implement other interfaces.
B.
Interfaces can have instance variables.
C.
Interfaces can define private methods.
D.
Interfaces can only declare abstract methods. A. C

Quiz

10/10
Which command-line argument instructs the javac compiler to produce a modular JAR file?
Select the answer
1 correct answer
A.
-cp <classpath>
B.
--module-source <version
C.
-module-path <modulepath>
D.
--module <module-name> A. B
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  • Quiz name:Java SE 21 Developer Professional
  • Total number of questions:116
  • Number of questions for the test:50
  • Pass score:80%

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