Precautions
No.1
data = (E[]) new Object[Capacity+1];Brackets
No.2
if(index < 0 || index >= size)
throw new IllegalArgumentException("Set failed. Index is illegal.");
Pay attention to the format of the exception thrown
No.3
//进队enqueue片段
data[tail] = e;
tail=(tail+1)% data.length;
size++;
//出队dequeue片段
E temp = data[front];
data[front]=null;
front=(front+1)% data.length;
size--;
The front and tail
queues of the circular queue are empty: front==tail
queue is full: (tail+1)% data.length
No.4
Pay attention to the format
//重写toString方法片段
StringBuilder res = new StringBuilder();
res.append(String.format("LoopQueue : size = %d , capacity = %d\n", size, getCapacity()));
Queue interface (source code)
public interface Queue<E> {
int getSize();
boolean isEmpty();
int getCapacity();
E dequeue();
E getFront();
void enqueue(E e);
}
ArrayQueue (source code)
public class ArrayQueue<E> implements Queue<E> {
private Array<E> array ;
public ArrayQueue(int Capacity){
array = new Array<>(Capacity);
}
public ArrayQueue(){
array = new Array<>();
}
@Override
public int getSize() {
return array.getSize();
}
@Override
public boolean isEmpty() {
return array.isEmpty();
}
@Override
public int getCapacity() {
return array.getCapacity();
}
@Override
public E getFront() {
return array.get(0);
}
@Override
public E dequeue() {
return array.delete(0);
}
@Override
public void enqueue(E e) {
array.addLast(e);
}
@Override
public String toString(){
StringBuilder res = new StringBuilder();
res.append("Queue:front ");
res.append("[");
for(int i = 0 ; i < array.getSize(); i ++){
res.append(array.get(i));
if(i!= array.getSize()-1)
res.append(", ");
}
res.append("] tail");
return res.toString();
}
}
LoopQueue (source code)
public class LoopQueue<E> implements Queue<E>{
private E[] data;
private int front,tail;
private int size;
public LoopQueue(int Capacity){
data = (E[]) new Object[Capacity+1];//!!!!!!!!!!!
front=0;
tail=0;
size=0;
}
public LoopQueue(){
this(10);
}
@Override
public int getSize() {
return size;
}
@Override
public boolean isEmpty() {
return front == tail;
}
@Override
public int getCapacity() {
return data.length-1;
}
@Override
public E dequeue() {
if(isEmpty())
throw new IllegalArgumentException("Cannot dequeue from an empty queue.");
E temp = data[front];
data[front]=null;
front=(front+1)% data.length;
size--;
if(size == getCapacity() / 4 && getCapacity() / 2 != 0)
resize(getCapacity() / 2);
return temp;
}
@Override
public void enqueue(E e) {
if((tail + 1) % data.length == front)
resize(getCapacity() * 2);
data[tail] = e;
tail=(tail+1)% data.length;
size++;
}
@Override
public E getFront() {
if(isEmpty())
throw new IllegalArgumentException("Cannot dequeue from an empty queue.");
return data[front];
}
private void resize(int newCapacity){
E[] newData = (E[])new Object[newCapacity + 1];
for(int i = 0 ; i < size ; i ++)
newData[i] = data[(i + front) % data.length];
data = newData;
front = 0;
tail = size;
}
@Override
public String toString() {
StringBuilder res = new StringBuilder();
res.append(String.format("LoopQueue : size = %d , capacity = %d\n", size, getCapacity()));
res.append("front [");
for (int i = front ; i != tail ; i = (i + 1) % data.length ){
res.append(data[i]);
if((i+1)% data.length != tail)
res.append(" , ");
}
res.append("] tail");
return res.toString();
}
}
main function
ArrayQueue test main function
public static void main(String[] args){
ArrayQueue<Integer> queue = new ArrayQueue<>();
for(int i = 0 ; i < 10 ; i ++){
queue.enqueue(i);
System.out.println(queue);
if(i % 3 == 2){
queue.dequeue();
System.out.println(queue);
}
}
}
LoopQueue test main function
public static void main(String[] args) {
LoopQueue<Integer> queue = new LoopQueue<>();
for (int i = 0; i < 5; i++) {
queue.enqueue(i);
System.out.println(queue);
if(i % 3 == 2){
queue.dequeue();
System.out.println(queue);
}
}
}
Test the difference between the two
Source code
import java.util.Random;
public class Main {
// 测试使用q运行opCount个enqueueu和dequeue操作所需要的时间，单位：秒
private static double testQueue(Queue<Integer> q, int opCount){
long startTime = System.nanoTime();
Random random = new Random();
for(int i = 0 ; i < opCount ; i ++)
q.enqueue(random.nextInt(Integer.MAX_VALUE));
for(int i = 0 ; i < opCount ; i ++)
q.dequeue();
long endTime = System.nanoTime();
return (endTime - startTime) / 1000000000.0;
}
public static void main(String[] args) {
int opCount = 100000;
ArrayQueue<Integer> arrayQueue = new ArrayQueue<>();
double time1 = testQueue(arrayQueue, opCount);
System.out.println("ArrayQueue, time: " + time1 + " s");
LoopQueue<Integer> loopQueue = new LoopQueue<>();
double time2 = testQueue(loopQueue, opCount);
System.out.println("LoopQueue, time: " + time2 + " s");
}
}
result
"C:\Program Files\Java\jdk14\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2020.2\lib\idea_rt.jar=56799:C:\Program Files\JetBrains\IntelliJ IDEA 2020.2\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\12778\IdeaProjects\first\out\production\Array com.Queue.main
ArrayQueue, time: 53.0073206 s
LoopQueue, time: 0.0352907 s
Process finished with exit code 0