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| Section | Weight | Objectives |
|---|---|---|
| Java I/O and Localization | 5% | - Resource bundles, locale, formatting messages, numbers, dates - File I/O, NIO.2, streams, readers/writers, serialization |
| Handling Date, Time, Text, Numeric and Boolean Values | 12% | - Use Date-Time API: LocalDate, LocalTime, LocalDateTime, Period, Duration, Instant, ZonedDateTime - Use primitives and wrapper classes, evaluate expressions and apply type conversions - Manipulate text, text blocks, String, StringBuilder and StringBuffer |
| Functional Programming and Streams | 15% | - Optional class, primitive streams - Lambda expressions, functional interfaces, method references - Stream API: create, intermediate/terminal operations, parallel streams, grouping, partitioning |
| Modules and Packaging | 5% | - Create and use JAR files, modular and non-modular builds - Module system: module-info.java, exports, requires, provides, uses |
| Using Object-Oriented Concepts | 20% | - Enums, nested classes, local variable type inference - Inheritance, abstract classes, sealed classes, interfaces, polymorphism - Overloading, overriding, Object class methods, immutable objects - Classes, records, objects, constructors, initializers, methods, fields, encapsulation |
| Controlling Program Flow | 10% | - Decision constructs: if-else, switch expressions and statements, pattern matching - Loops: for, enhanced for, while, do-while, break, continue, return |
| Handling Exceptions | 8% | - Exception hierarchy, try-catch-finally, multi-catch, try-with-resources - Create and use custom exceptions, throw, throws |
| Advanced Features and Annotations | 3% | - Generics, type parameters, wildcards, type erasure - Annotations, built-in annotations, custom annotations |
| Concurrency and Multithreading | 10% | - Thread lifecycle, Runnable, Callable, ExecutorService, virtual threads - Synchronization, locks, concurrent collections, thread safety |
| Working with Arrays and Collections | 12% | - Declare, instantiate, initialize, use arrays and multidimensional arrays - Collections Framework: List, Set, Map, Deque, Queue, sorting, searching |
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NEW QUESTION # 77
Given:
java
List<Integer> integers = List.of(0, 1, 2);
integers.stream()
.peek(System.out::print)
.limit(2)
.forEach(i -> {});
What is the output of the given code fragment?
Answer: E
Explanation:
In this code, a list of integers integers is created containing the elements 0, 1, and 2. A stream is then created from this list, and the following operations are performed in sequence:
* peek(System.out::print):
* The peek method is an intermediate operation that allows performing an action on each element as it is encountered in the stream. In this case, System.out::print is used to print each element.
However, since peek is intermediate, the printing occurs only when a terminal operation is executed.
* limit(2):
* The limit method is another intermediate operation that truncates the stream to contain no more than the specified number of elements. Here, it limits the stream to the first 2 elements.
* forEach(i -> {}):
* The forEach method is a terminal operation that performs the given action on each element of the stream. In this case, the action is an empty lambda expression (i -> {}), which does nothing for each element.
The sequence of operations can be visualized as follows:
* Original Stream Elements: 0, 1, 2
* After peek(System.out::print): Elements are printed as they are encountered.
* After limit(2): Stream is truncated to 0, 1.
* After forEach(i -> {}): No additional action; serves to trigger the processing.
Therefore, the output of the code is 01, corresponding to the first two elements of the list being printed due to the peek operation.
NEW QUESTION # 78
Given a properties file on the classpath named Person.properties with the content:
ini
name=James
And:
java
public class Person extends ListResourceBundle {
protected Object[][] getContents() {
return new Object[][]{
{"name", "Jeanne"}
};
}
}
And:
java
public class Test {
public static void main(String[] args) {
ResourceBundle bundle = ResourceBundle.getBundle("Person");
String name = bundle.getString("name");
System.out.println(name);
}
}
What is the given program's output?
Answer: C
Explanation:
In this scenario, we have a Person class that extends ListResourceBundle and a properties file named Person.
properties. Both define a resource with the key "name" but with different values:
* Person class (ListResourceBundle):Defines the key "name" with the value "Jeanne".
* Person.properties file:Defines the key "name" with the value "James".
When the ResourceBundle.getBundle("Person") method is called, the Java runtime searches for a resource bundle with the base name "Person". The search order is as follows:
* Class-Based Resource Bundle:The runtime first looks for a class named Person (i.e., Person.class).
* Properties File Resource Bundle:If the class is not found, it then looks for a properties file named Person.properties.
In this case, since the Person class is present and accessible, the runtime will load the Person class as the resource bundle. Therefore, the getBundle method returns an instance of the Person class.
Subsequently, when bundle.getString("name") is called, it retrieves the value associated with the key "name" from the Person class, which is "Jeanne".
Thus, the output of the program is:
nginx
Jeanne
NEW QUESTION # 79
Given:
java
String colors = "red\n" +
"green\n" +
"blue\n";
Which text block can replace the above code?
Answer: E
Explanation:
* Understanding Multi-line Strings in Java (""" Text Blocks)
* Java 13 introducedtext blocks ("""), allowing multi-line stringswithout needing explicit \n for new lines.
* In a text block,each line is preserved as it appears in the source code.
* Analyzing the Options
* Option A: \ (Backslash Continuation)
* The backslash (\) at the end of a lineprevents a new line from being added, meaning:
nginx
red green blue
* Incorrect.
* Option B: \s (Whitespace Escape)
* \s represents asingle space,not a new line.
* The output would be:
nginx
red green blue
* Incorrect.
* Option C: \t (Tab Escape)
* \t inserts atab, not a new line.
* The output would be:
nginx
red green blue
* Incorrect.
* Option D: Correct Text Block
java
String colors = """
red
green
blue
""";
* Thispreserves the new lines, producing:
nginx
red
green
blue
* Correct.
Thus, the correct answer is:"String colors = """ red green blue """."
References:
* Java SE 21 - Text Blocks
* Java SE 21 - String Formatting
NEW QUESTION # 80
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?
Answer: C
Explanation:
In this code, a double variable amount is initialized to 42,000.00. The NumberFormat.
getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.SHORT) method is used to obtain a compact number formatter for the French locale with the short style. The format method is then called to format the amount.
The compact number formatting is designed to represent numbers in a shorter form, based on the patterns provided for a given locale. In the French locale, the short style represents thousands with a lowercase 'k'.
Therefore, 42,000 is formatted as 42 k.
* Option Evaluations:
* A. 42000E: This format is not standard in the French locale for compact number formatting.
* B. 42 000,00 €: This represents the number as a currency with two decimal places, which is not the compact form.
* C. 42000: This is the plain number without any formatting, which does not match the compact number format.
* D. 42 k: This is the correct compact representation of 42,000 in the French locale with the short style.
Thus, option D (42 k) is the correct output.
NEW QUESTION # 81
Given:
java
try (FileOutputStream fos = new FileOutputStream("t.tmp");
ObjectOutputStream oos = new ObjectOutputStream(fos)) {
fos.write("Today");
fos.writeObject("Today");
oos.write("Today");
oos.writeObject("Today");
} catch (Exception ex) {
// handle exception
}
Which statement compiles?
Answer: B
Explanation:
In Java, FileOutputStream and ObjectOutputStream are used for writing data to files, but they have different purposes and methods. Let's analyze each statement:
* fos.write("Today");
The FileOutputStream class is designed to write raw byte streams to files. The write method in FileOutputStream expects a parameter of type int or byte[]. Since "Today" is a String, passing it directly to fos.
write("Today"); will cause a compilation error because there is no write method in FileOutputStream that accepts a String parameter.
* fos.writeObject("Today");
The FileOutputStream class does not have a method named writeObject. The writeObject method is specific to ObjectOutputStream. Therefore, attempting to call fos.writeObject("Today"); will result in a compilation error.
* oos.write("Today");
The ObjectOutputStream class is used to write objects to an output stream. However, it does not have a write method that accepts a String parameter. The available write methods in ObjectOutputStream are for writing primitive data types and objects. Therefore, oos.write("Today"); will cause a compilation error.
* oos.writeObject("Today");
The ObjectOutputStream class provides the writeObject method, which is used to serialize objects and write them to the output stream. Since String implements the Serializable interface, "Today" can be serialized.
Therefore, oos.writeObject("Today"); is valid and compiles successfully.
In summary, the only statement that compiles without errors is oos.writeObject("Today");.
References:
* Java SE 21 & JDK 21 - ObjectOutputStream
* Java SE 21 & JDK 21 - FileOutputStream
NEW QUESTION # 82
......
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