public class LinkQueue<T> {
// Define the inner class Node, the Node instance represents the node of the chain queue
private class Node {
// save the node data
private T data;
// a reference to the next node
private Node next;
// constructor with no arguments
public Node() {
}
// initialize the constructor for all properties
public Node(T data, Node next) {
this.data = data;
this.next = next;
}
}
// Save the head node of the chain queue
private Node front;
// Save the tail node of the chain queue
private Node rear;
// Save the number of nodes already contained in the chain queue
private int size;
// create empty chain queue
public LinkQueue() {
// empty chain queue, front and rear are null
front = null;
rear = null;
}
// Create a chain queue with the specified data element, the chain queue has only one element
public LinkQueue(T element) {
front = new Node(element, null);
// There is only one node, both front and rear point to this node
rear = front;
size++;
}
// return the length of the chain queue
public int length() {
return size;
}
// add the new element to the queue
public void add(T element) {
// If the chain queue is still an empty chain queue
if (front == null) {
front = new Node(element, null);
// There is only one node, front and rear all point to this node
rear = front;
} else {
// create new node
Node newNode = new Node(element, null);
// Let the next of the tail node point to the new node
rear.next = newNode;
// use the new node as the new tail node
rear = newNode;
}
size++;
}
// delete the element on the front side of the queue
public T remove() {
Node oldFront = front;
front = front.next;
oldFront.next = null;
size--;
return oldFront.data;
}
// access the last element in the chained queue
public T element() {
return rear.data;
}
// Determine if the chained queue is empty
public boolean empty() {
return size == 0;
}
// clear the chain
public void clear() {
// Assign the front and rear nodes to null
front = null;
rear = null;
size = 0;
}
public String toString() {
if (empty()) {
return "[]";
} else {
StringBuilder sb = new StringBuilder("[");
for (Node current = front; current != null; current = current.next) {
sb.append(current.data.toString() + ", ");
}
int len = sb.length();
return sb.delete(len - 2, len).append("]").toString();
}
}
}
public class LinkQueueTest {
public static void main(String[] args) {
LinkQueue<String> queue = new LinkQueue<String>("aaaa");
queue.add("bbbb");
queue.add("cccc");
System.out.println("Chain queue initialization element: " + queue.toString());
queue.remove();
System.out.println("Queue after deleting an element: " + queue.toString());
queue.add("dddd");
System.out.println("Queue after adding elements again: " + queue);
queue.remove();
queue.add("eeee");
System.out.println(queue);
}
}