public class SequenceQueue<T> {
private int DEFAULT_SIZE = 10;
// save the length of the array
private int capacity;
// Define an array to hold the elements of the sequential queue
private Object[] elementData;
// Save the current number of elements in the sequential queue
private int front = 0;
private int rear = 0;
// Create empty sequential queue with default array length
public SequenceQueue() {
capacity = DEFAULT_SIZE;
elementData = new Object[capacity];
}
// create a sequential queue with an initializer element
public SequenceQueue(T element) {
this();
elementData[0] = element;
rear++;
}
/**
* Create a sequential queue with an array of specified length
* @param element specifies the first element in the sequence queue
* @param initSize specifies the length of the underlying array of the sequential queue
*/
public SequenceQueue(T element, int initSize) {
this.capacity = initSize;
elementData = new Object[capacity];
elementData[0] = element;
rear++;
}
// Get the size of the sequential queue
public int length() {
return rear -front;
}
// Determine if the sequence queue is empty
public boolean empty() {
return rear == front;
}
// insert into the queue
public void add(T element) {
if (rear > capacity - 1) {
throw new IndexOutOfBoundsException("Queue full exception");
}
elementData[rear++] = element;
}
// remove queue
public T remove() {
if (empty()) {
throw new IndexOutOfBoundsException("empty queue exception");
}
// retain the value of the element on the rear side of the queue
T oldValue = (T)elementData[front];
// Release the element on the rear side of the queue
elementData[front++] = null;
return oldValue;
}
// Return the top element of the queue, but do not delete the top element of the queue
public T element() {
if (empty()) {
throw new IndexOutOfBoundsException("empty queue exception");
}
return (T)elementData[front];
}
// clear the sequence queue
public void clear() {
Arrays.fill(elementData, null);
front = 0;
rear = 0;
}
public String toString() {
if (empty()) {
return "[]";
} else {
StringBuilder sb = new StringBuilder("[");
for (int i = front; i < rear; i++) {
sb.append(elementData[i].toString() + ", ");
}
int len = sb.length();
return sb.delete(len - 2, len).append("]").toString();
}
}
}
public class SequenceQueueTest {
public static void main(String[] args) {
SequenceQueue<String> queue = new SequenceQueue<String>();
queue.add("aaaa");
queue.add("bbbb");
queue.add("cccc");
queue.add("dddd");
System.out.println("Sequential queue initialization element: " + queue.toString());
System.out.println("Access the front-end element of the sequential queue: " + queue.element());
System.out.println("Remove the front element of the sequence queue: " + queue.remove());
System.out.println("After removing the front element for the first time: " + queue.toString());
System.out.println("Remove the front element of the sequence queue: " + queue.remove());
System.out.println("After removing the front element for the second time: " + queue.toString());
}
}