java自定义栈(数组实现)

这里是使用Object数组来实现栈的存取，由于栈的FILO的特性，其用链表更加节省空间；

首先定义一个栈接口，用来描述栈的功能，提供出栈、入栈、获取栈顶元素、判断是否为空以及清空栈；

package my.stack;

public interface IStack<T> {
	//元素出栈，并返回出栈元素
	public T pop();
	
	//元素入栈
	public void push(T element);
	
	//获取栈顶元素
	public T peek();
	
	//判断栈是否为空
	public boolean isEmpty();
	
	public void clear();
}

---

然后，根据栈接口的描述来实现该栈，这里用Object数组的方式来实现;

package my.stack;

import java.util.Arrays;

public class ArrayStack<T> implements IStack<T> {
	private final int DEFAULT_SIZE = 3;
	private int size = 0;
	private int capacity = 0;
	
	//top指向下一个能够添加元素的位置
	private int top = 0;
	private Object[] array;
	
	public ArrayStack(){
		this.capacity = this.DEFAULT_SIZE;
		this.array = new Object[this.capacity];
		this.size = 0;
	}
	
	public ArrayStack(int capacity){
		this.capacity = capacity;
		this.array = new Object[this.capacity];
		this.size = 0;
	}
	
	@Override
	public boolean isEmpty() {
		// TODO Auto-generated method stub
		return size == 0;
	}

	@Override
	public T peek() {
		// TODO Auto-generated method stub
		return (T)this.array[this.top-1];
	}

	@Override
	public T pop() {
		// TODO Auto-generated method stub
		T element = (T)this.array[top - 1];
		this.array[top-1] = null;
		this.size--;
		return element;
	}

	@Override
	public void push(T element) {
		// TODO Auto-generated method stub
		if(this.size < this.capacity){
			this.array[top] = element;
			this.top++;
			this.size ++;
		}else{
//			System.out.println("out of array");
			enlarge();
			push(element);
		}
	}
	
	public void enlarge(){
		this.capacity = this.capacity + this.DEFAULT_SIZE;
		Object[] newArray = new Object[this.capacity];
		System.arraycopy(array, 0, newArray, 0, array.length);
		Arrays.fill(array, null);
		this.array = newArray;
	}
	
	public int size(){
		return this.size;
	}

	@Override
	public void clear() {
		// TODO Auto-generated method stub
		Arrays.fill(array, null);
		this.top = 0;
		this.size = 0;
		this.capacity = this.DEFAULT_SIZE;
		this.array = new Object[this.capacity];
	}
}

---

最后编写一个测试客户端，用来测试该栈能够正常工作;

package my.stack;

public class MyArrayStackClient {
	public static void main(String[] args) {
		ArrayStack<Integer> stack = new ArrayStack<Integer>();
		stack.push(1);
		stack.push(2);
		stack.push(3);
		stack.push(4);
		stack.push(5);
		System.out.println(stack.isEmpty());
		System.out.println(stack.peek());
//		System.out.println(stack.pop());
		System.out.println(stack.size());
		stack.clear();
		System.out.println(stack.size());
	}

}