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BAEL-5699 (#12674) 

* BAEL-5699

First draft of the article example

* BAEL-5699

Removed unused class FifoFixedSizeQueueRemoveOldestInOffer.java
Removed unused UnitTest for the removed class
Added some tests to check count attribute
This commit is contained in:
victorsempere 2022-09-15 21:04:23 +02:00 committed by GitHub
parent f8ea63de51
commit 171e4bd7c8
2 changed files with 212 additions and 0 deletions
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79
core-java-modules/core-java-collections-4/src/main/java/com/baeldung/collections/fixedsizequeues/FifoFixedSizeQueue.java Normal file
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package com.baeldung.collections.fixedsizequeues;
import java.util.AbstractQueue;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class FifoFixedSizeQueue<E> extends AbstractQueue<E> {
/** The queued items */
final Object[] items;
/** Number of elements in the queue */
int count;
public FifoFixedSizeQueue(int capacity) {
super();
items = new Object[capacity];
count = 0;
}
@Override
public boolean offer(E e) {
if (e == null) {
throw new NullPointerException("Queue doesn't allow nulls");
}
if (count == items.length) {
this.poll();
}
this.items[count] = e;
count++;
return true;
}
@Override
public E poll() {
if (count <= 0) {
return null;
}
E item = (E) items[0];
shiftLeft();
count--;
return item;
}
private void shiftLeft() {
int i = 1;
while (i < items.length) {
if (items[i] == null) {
break;
}
items[i - 1] = items[i];
i++;
}
}
@Override
public E peek() {
if (count <= 0) {
return null;
}
return (E) items[0];
}
@Override
public int size() {
return count;
}
@Override
public Iterator<E> iterator() {
List<E> list = new ArrayList<>(count);
for (int i = 0; i < count; i++) {
list.add((E) items[i]);
}
return list.iterator();
}
}

133
core-java-modules/core-java-collections-4/src/test/java/com/baeldung/collections/fixedsizequeues/FifoFixedSizeQueueUnitTest.java Normal file
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package com.baeldung.collections.fixedsizequeues;
import java.util.Iterator;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNull;
public class FifoFixedSizeQueueUnitTest {
@Test
void givenEmptyQueue_whenIterating_thenHasNextIsFalse() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
Iterator<String> i = toTest.iterator();
assertFalse(i.hasNext());
}
@Test
void givenEmptyQueue_whenOffer_thenCountIsOne() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
toTest.offer("1");
assertEquals(1, toTest.size());
}
@Test
void givenEmptyQueue_whenPeek_thenNull() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
String tail = toTest.peek();
assertNull(tail);
}
@Test
void givenEmptyQueue_whenPoll_thenNull() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
String dequeued = toTest.poll();
assertNull(dequeued);
}
@Test
void givenNonEmptyQueue_whenIterating_thenHasNextIsTrue() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
Iterator<String> i = toTest.iterator();
assertFalse(i.hasNext());
}
@Test
void givenNonEmptyQueue_whenOffer_thenCountMatchesQueueElements() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
toTest.offer("1");
toTest.offer("2");
assertEquals(2, toTest.size());
}
@Test
void givenNonEmptyQueue_whenPeek_thenFirstElementMustBeReturned() {
String expectedElement = "1";
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
toTest.offer(expectedElement);
toTest.offer("2");
assertEquals(expectedElement, toTest.peek());
assertEquals(expectedElement, toTest.peek());
}
@Test
void givenNonEmptyQueue_whenPoll_thenFirstElementMustBeReturnedAndRemoved() {
String expectedPoll = "1";
String expectedTailAfterPoll = "2";
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(10);
toTest.offer(expectedPoll);
toTest.offer(expectedTailAfterPoll);
assertEquals(expectedPoll, toTest.poll());
assertEquals(expectedTailAfterPoll, toTest.peek());
}
@Test
void givenFullQueue_whenOffer_thenRemovedOldestFromTailAndOffer() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(2);
toTest.offer("1");
toTest.offer("2");
toTest.offer("3");
Iterator<String> i = toTest.iterator();
assertEquals("2", i.next());
assertEquals("3", i.next());
assertFalse(i.hasNext());
}
@Test
void whenPoll_thenSizeDecreases() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(2);
toTest.offer("1");
toTest.poll();
assertEquals(0, toTest.size());
}
@Test
void whenOffer_thenSizeIncreases() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(2);
toTest.offer("1");
assertEquals(1, toTest.size());
}
@Test
void givenFullQueue_whenOffer_thenElementIsInsertedAndSizeEqualsCapacity() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(2);
toTest.offer("1");
toTest.offer("2");
toTest.offer("3");
assertEquals(2, toTest.size());
assertEquals("2", toTest.peek());
}
@Test
void givenEmptyQueue_whenSizeRequest_thenZero() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(2);
assertEquals(0, toTest.size());
}
@Test
void givenEmptyQueue_whenPoll_thenReturnNullAndSizeIsZero() {
FifoFixedSizeQueue<String> toTest = new FifoFixedSizeQueue<>(2);
assertNull(toTest.poll());
assertEquals(0, toTest.size());
}
}