Quiz

Java Intermediate

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Quiz

Question 1

What is the difference between the peek() and element() methods in a queue?

peek() returns null if the queue is empty, while element() throws an exception.

peek() removes the head element, while element() does not.

element() returns null if the queue is empty, while peek() throws an exception.

Both methods behave identically.

Question 2

Examine the following code snippet using PriorityQueue:

import java.util.PriorityQueue;

public class Test {
    public static void main(String[] args) {
        PriorityQueue<Integer> numbers = new PriorityQueue<>();
        numbers.add(20);
        numbers.add(5);
        numbers.add(15);
        numbers.add(10);
        System.out.println("PriorityQueue: " + numbers);
        Integer head = numbers.poll();
        System.out.println("Polled Element: " + head);
    }
}

What will the PriorityQueue output and which element is polled?

PriorityQueue: [20, 5, 15, 10]; Polled Element: 20

PriorityQueue: [10, 15, 20, 5]; Polled Element: 10

PriorityQueue: [15, 10, 5, 20]; Polled Element: 15

PriorityQueue: [5, 10, 15, 20]; Polled Element: 5

Question 3

Consider the following code snippet using ArrayDeque as a stack:

import java.util.ArrayDeque;

public class Test {
    public static void main(String[] args) {
        ArrayDeque<String> stack = new ArrayDeque<>();
        stack.addFirst("Plate 1");
        stack.addFirst("Plate 2");
        stack.addFirst("Plate 3");
        System.out.println("Stack: " + stack);
        String top = stack.removeFirst();
        System.out.println("Popped: " + top);
        System.out.println("Stack after pop: " + stack);
    }
}

What behavior is demonstrated by this code?

FIFO behavior (queue).

LIFO behavior (stack).

Random removal of elements.

Sorted order of elements.

.....

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