java使用数组实现顺序队列

Posted 2022-12-03 CLAY&Loser

package com.Alg;

import java.io.Serializable;
import java.util.Arrays;

/**
 * @ClassName SequentialQueue
 * @author sunyu
 * @Description 顺序队列
 * @param <T>
 */
public class SequentialQueue<T> implements Serializable 
	private static final long serialVersionUID = 1L;
	private int DEFAULT_SIZE = 10;
	private int capacity; // 保存数组的长度
	private Object[] elementData;// 定义一个数组用于保存顺序队列的元素
	private int fornt = 0;// 队列头
	private int rear = 0;// 队列尾

	// 无参数构造，以默认参数创建空顺序队列
	public SequentialQueue() 
		capacity = DEFAULT_SIZE;
		elementData = new Object[capacity];
	

	// 有参构造，以一个初始化元素来创建顺序队列
	public SequentialQueue(T element) 
		this();// 调用午餐构造器
		elementData[0] = element;
		rear++;
	

	// 有参构造，指定队列大小构造空顺序队列
	public SequentialQueue(int initSize) 
		elementData = new Object[initSize];
	

	/**
	 * 以指定长度的数组来创建顺序队列
	 * 
	 * @param element
	 *            指定顺序队列中第一个元素
	 * @param initSize
	 *            指定顺序队列底层数组的长度
	 */
	public SequentialQueue(T element, int initSize) 
		this.capacity = initSize;
		elementData = new Object[capacity];
		elementData[0] = element;
		rear++;
	

	/**
	 * @Title: size
	 * @Description: 获取顺序队列大小
	 * @return
	 */
	public int size() 
		return rear - fornt;
	

	public void offer(T element) 
		ensureCapacity(rear + 1);
		elementData[rear++] = element;
	

	/**
	 * @Description: 确认数组的长度是否满足新元素的添加，不满足时扩充数组
	 * @param minCapacity
	 */
	public void ensureCapacity(int minCapacity) 
		int oldCapacity = elementData.length;
		if (minCapacity > oldCapacity) 
			int newCapacity = (oldCapacity * 3) / 2 + 1;
			if (newCapacity < minCapacity) 
				newCapacity = minCapacity;
				// 复制指定的数组，截取或用 null 填充（如有必要），以使副本具有指定的长度。
				elementData = Arrays.copyOf(elementData, newCapacity);
			
		
	

	/**
	 * @Description: 出队
	 * @return
	 */

	public T poll() 
		if (isempty()) 
			throw new IndexOutOfBoundsException("空队列异常");
		
		// 保留队列的fornt端的元素值
		T oldvalue = (T) elementData[fornt];
		// 释放队列的fornt端的元素
		elementData[fornt++] = null;
		return oldvalue;
	

	/**
	 * @Description: 判断队列是否为空
	 * @return
	 */
	private boolean isempty() 
		return fornt == rear;
	

	/**
	 * @Description: 返回队列顶元素，但不删除队列顶元素
	 * @return
	 */
	public T peek() 
		if (isempty()) 
			throw new IndexOutOfBoundsException("空队列异常");
		
		return (T) elementData[fornt];
	

	/**
	 * @Title: clear
	 * @Description: 清空顺序队列
	 * @return
	 */
	public void clear() 
		// 将指定的null值分配给指定数组指定范围中的每个元素
		Arrays.fill(elementData, null);
		fornt = 0;
		rear = 0;
	

	public String toString() 
		if (isempty()) 
			return "[]";
		 else 
			StringBuilder sb = new StringBuilder("[");
			for (int i = fornt; i < rear; i++) 
				sb.append(elementData[i].toString() + ", ");
			
			int len = sb.length();
			return sb.delete(len - 2, len).append("]").toString();
		
	

	public static void main(String[] args) 
		SequentialQueue<String> sq = new SequentialQueue<String>();
		sq.offer("1");
		sq.offer("2");
		sq.offer("3");
		System.out.println(sq.toString());