在 java 中显示循环队列

Question

我有以下代码，我在其中实现了一个循环数组。 当我尝试显示它时，问题就来了。 display 方法运行良好，直到数组变满并且 last 回到 0。因此 last 和 first 都是 0 并且 for 循环不执行。

public class PassengerQueue 
{

private Passenger[] queueArray = new Passenger[TrainStation.WAITING_ROOM_CAPACITY];
private int first = 0;
private int last = 0;
private int maxStayInQueue = 0; //number of seconds that the passenger who stayed longest in the queue
private int maxLength = 0; //the maximum legth that was reached by the queue
private int currentSize = 0;

public void add(Passenger next)
{
    //if the queue is not full - check for the circular queue
    if (isFull()){
        System.out.println("The queue is full");
    }
    else
    {

        queueArray[last] = next; 
        last = (last + 1) % queueArray.length;

        currentSize++;
        maxLength++;

    }

}

public Passenger remove()
{
    Passenger removedPassenger = null;
    //if the queue array is not empty
    //remove passenger
    if (isEmpty())
    {
        System.out.println("The queue is empty");
    }
    else
    {
        removedPassenger = queueArray[first];
        queueArray[first] = null;
        first = (first + 1) % queueArray.length;
        currentSize--;

    }
    return removedPassenger;
}   

public Boolean isEmpty()
{
    return (currentSize == 0);
}

public Boolean isFull()
{
    return (currentSize == queueArray.length);
}


public void display()
{
    if (isEmpty())
    {
        System.out.println("The queue is empty");
    }
    else
    {
        for(int i = first; i < last; i++)
        {
            queueArray[i].display();
        }
    }
}

任何帮助，将不胜感激！ 谢谢你

Answer 1

只需使用数组本身的属性来显示：

public void display()
{
    if (isEmpty())
    {
        System.out.println("The queue is empty");
    }
    else
    {
        for(int i = 0; i < queueArray.length; i++)
        {
            queueArray[i].display();
        }
    }
}

Answer 2

您可以更改循环，使其从 0 迭代到 size。 这也解决了last小于first的问题，因为项目已被删除。

    for(int i = 0; i < currentSize; i++)
    {
        queueArray[(first + i) % queueArray.length].display();
    }