此处包括一个泛型顺序队列抽象类，一个Integer型实现类，一个测试类。

实现了队列的以下功能：

1.队尾入队

2.队首出队

3.取队首

4.判空

5.求长度

6.删除队首元素

7.扩充长度

泛型顺序队列抽象类

Queue.java：

package queue;

import java.lang.reflect.Array;
import java.util.Arrays;

public abstract class Queue<T> {

	protected int front;
	protected int rear;
	protected T[] arr;
	private int maxSize;
	
	public Queue(Class<T> componentType) {
		this.front = 0;
		this.rear = 0;
		this.maxSize = 1024;
		arr = (T[])Array.newInstance(componentType, this.maxSize);
	}
	
	public Queue(Class<T> componentType, int maxSize) {
		this.front = 0;
		this.rear = 0;
		this.maxSize = maxSize;
		arr = (T[])Array.newInstance(componentType, this.maxSize);
	}
	
	public int getSize() {
		return this.rear - this.front;
	}
	
	public void expandMaxSize(int maxSize) {
		Arrays.copyOf(arr, this.maxSize + maxSize);
		this.maxSize += maxSize;
	}

	
	public void offer(T data) {
		if(this.getSize() > this.maxSize || this.rear > this.maxSize) {
			throw new IllegalArgumentException("new element will be out of limits.");
		}
		arr[this.rear++] = data;
	}
	
	public void remove() {
		if(this.front == this.rear) {
			throw new IllegalArgumentException("this queue is already empty");
		}
		this.front++;
	}
	
	public T peek() {
		if(this.front == this.rear) {
			throw new IllegalArgumentException("this queue is already empty");
		}
		return arr[this.front];
	}
	
	public T poll() {
		if(this.front == this.rear) {
			throw new IllegalArgumentException("this queue is already empty");
		}	
		return arr[this.front++];
	}

	
}

Integer型实现类

IntegerQueue.java：

package queue;

public class IntegerQueue extends Queue<Integer> {

	public IntegerQueue() {
		super(Integer.class);
	}

	public IntegerQueue(int maxSize) {
		super(Integer.class, maxSize);
	}
	
	public void print(){
		System.out.print("F-");
		for(int i = this.rear - 1; i >= this.front; i--) {
			System.out.print(arr[i] + "-");
		}
		System.out.println("R");
	}

}

 测试类

IntegerQueueDemo：

package queue;

public class IntegerQueueDemo {

	public static void main(String[] args) {
		IntegerQueue test = new IntegerQueue();
		test.print();
		System.out.println("size is: " + test.getSize());
		System.out.println("================");	

		test.offer(8);
		test.offer(14);
		test.offer(5);
		test.offer(3);
		test.print();
		System.out.println("size is: " + test.getSize());
		
		System.out.println("================");	
		
		System.out.println("the element in front of queue: " + test.peek());
		test.remove();
		test.print();
		System.out.println("size is: " + test.getSize());
		System.out.println("the element in front of queue: " + test.peek());
		
		System.out.println("================");	
		
		System.out.println("the fetched element: " + test.poll());
		test.print();
		System.out.println("size is: " + test.getSize());
		System.out.println("the element in front of queue: " + test.peek());
	}

}

 输出结果：

F-R
size is: 0
================
F-3-5-14-8-R
size is: 4
================
the element in front of queue: 8
F-3-5-14-R
size is: 3
the element in front of queue: 14
================
the fetched element: 14
F-3-5-R
size is: 2
the element in front of queue: 5