Explain what is meant by using parallel streams in Java and what are its advantages.

In Java, parallel streams are a way to execute multiple tasks simultaneously using multithreading. This allows the program to efficiently utilize CPU resources, especially on multi-core systems.

Advantages of using parallel streams:

• Speeding up task execution — tasks can run concurrently, reducing overall runtime.
• Increasing performance — effective use of multiple CPU cores.
• Application responsiveness — the interface can remain responsive while background tasks run in parallel.

Example of creating and starting a parallel thread:

Thread thread = new Thread(() -> {
    System.out.println("Executing in a separate thread");
});
thread.start();

Also, in Java 8+ there is a convenient way to process collections in parallel using the Stream API:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
int sum = numbers.parallelStream()
                 .mapToInt(Integer::intValue)
                 .sum();