What is the output of the following code?
import java.util.*;
public class Test {
public static void main(String[] args) {
List list = Arrays.asList("A", "B", "C");
list.add("D");
}
}
The Arrays.asList method returns a fixed-size list backed by the original array. Attempting to add elements to this list results in a UnsupportedOperationException at runtime. However, the code provided does not handle this exception, leading to a compilation error due to incorrect handling of the list's immutability.
Which interface in the Java Collections Framework represents a collection of elements that allows for duplicates and maintains insertion order?
The List interface represents a collection of elements that allows for duplicates and maintains the order of insertion. Examples include ArrayList and LinkedList. Set does not allow duplicates, Queue represents a collection designed for holding elements prior to processing, and Map represents a collection of key-value pairs.
Which of the following classes is part of the Java Collections Framework and provides constant-time performance for the basic operations?
HashSet is part of the Java Collections Framework and provides constant-time performance for basic operations like add, remove, contains, and size, assuming the hash function disperses elements properly among the buckets. ArrayList and LinkedList offer different performance characteristics for various operations, and TreeSet provides log(n) time complexity for basic operations.
How does the Java Streams API improve the processing of collections?
The Java Streams API allows for both sequential and parallel processing of elements. It provides a functional approach to processing collections, where operations can be performed in parallel to improve performance. Streams do not modify the original collection but instead produce a new stream with the processed results.
What does the "java.util.concurrent" package primarily provide?
he java.util.concurrent package provides utilities for concurrent programming and synchronization, including classes and interfaces for managing threads, task execution, synchronization, and concurrent data structures. It includes features like ExecutorService, ConcurrentHashMap, and CountDownLatch.