/
QueueTest.java
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/
QueueTest.java
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package util;
import org.junit.Test;
import java.util.LinkedList;
import java.util.NoSuchElementException;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.stream.IntStream;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;
import static org.junit.jupiter.api.Assertions.assertThrows;
public class QueueTest {
@Test
public void testQueue() {
{
Queue<Integer> queue = new LinkedList<>();
// add / remove / element
assertThrows(NoSuchElementException.class, queue::remove);
assertThrows(NoSuchElementException.class, queue::element);
IntStream.range(0, 10).forEach(queue::add);
assertThat(queue.toArray(), equalTo(new Integer[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}));
assertEquals(queue.element(), Integer.valueOf(0));
assertEquals(queue.remove(), Integer.valueOf(0));
}
{
Queue<Integer> queue = new LinkedList<>();
// offer / poll / peek
assertEquals(queue.poll(), null);
assertEquals(queue.peek(), null);
IntStream.range(0, 10).forEach(queue::offer);
assertThat(queue.toArray(), equalTo(new Integer[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}));
assertEquals(queue.peek(), Integer.valueOf(0));
assertEquals(queue.poll(), Integer.valueOf(0));
}
}
@Test
public void testPriorityQueue() {
{
PriorityQueue<Integer> pq = new PriorityQueue<>();
IntStream.range(0, 5).map(x -> 9 - x).forEach(pq::add);
IntStream.range(0, 5).forEach(pq::add);
for (int i = 0; i < 10; i++) {
assertEquals(pq.element(), Integer.valueOf(i));
assertEquals(pq.remove(), Integer.valueOf(i));
}
}
{
PriorityQueue<Integer> pq = new PriorityQueue<>((a, b) -> (b - a));
IntStream.range(0, 5).map(x -> 9 - x).forEach(pq::add);
IntStream.range(0, 5).forEach(pq::add);
for (int i = 9; i >= 0; i--) {
assertEquals(pq.element(), Integer.valueOf(i));
assertEquals(pq.remove(), Integer.valueOf(i));
}
}
}
@Test
public void testArrayBlockingQueue() {
Queue<Integer> queue = new ArrayBlockingQueue<>(10);
// empty
assertThrows(NoSuchElementException.class, queue::remove);
assertEquals(queue.poll(), null);
assertThrows(NoSuchElementException.class, queue::element);
assertEquals(queue.peek(), null);
IntStream.range(0, 10).forEach(queue::add);
// full
assertThrows(IllegalStateException.class, () -> queue.add(10));
assertFalse(queue.offer(10));
}
}