package com.yy.stack;


public class Stack {
	
	//陣列實現棧結構
	private Object[] obj;
	//棧的長度
	private int index;
	
	/**
	 * 初始化長度為10的棧
	 */
	public Stack() {
		obj = new Object[10];
	}
	
	/**
	 * 初始化長度為length的棧
	 * @param length
	 */
	public Stack(int length){
		obj = new Object[length];
	}
	
	/**
	 * 進棧
	 */
	public void push(Object o){
		expandStack();
		obj[index++] = o;
	}

	/**
	 * 出棧
	 */
	public void pop(){
		//1.先判斷陣列是否為空
		//2.出棧
		if(isEmpty()){
			System.out.println("棧為空");
		}else{
			Object[] temp = new Object[index--];
			System.arraycopy(obj, 0, temp, 0, index);
			obj = temp;
		}
	}
	
	/**
	 * 出棧並返回資料
	 * @return
	 */
	public Object getPop(){
		Object o = null;
		if(isEmpty()){
			System.out.println("棧為空");
		}else{
			o = getLast();
			Object[] temp = new Object[index--];
			System.arraycopy(obj, 0, temp, 0, index);
			obj = temp;
		}
		return o;
	}

	/**
	 * 獲取棧的最後一位資料
	 * @return
	 */
	public Object getLast() {
		int length = index;
		return obj[--length];
	}

	/**
	 * 判斷是否為空棧
	 * @return
	 */
	public boolean isEmpty() {
		if(index == 0){
			return true;
		}
		return false;
	}

	/**
	 * 
	 * 判斷棧的容量並擴大
	 */
	private void expandStack() {
		//判斷當前棧的長度是否滿了
		if(index >= obj.length){
			Object[] temp = new Object[obj.length * 2];
			System.arraycopy(obj, 0, temp, 0, obj.length);//陣列拷貝
			obj = temp;
		}
	}

	
	/**
	 * 獲取棧的長度
	 * @return
	 */
	public int getSize(){
		return index;
	}
	
	/**
	 * 列印棧
	 */
	public void printStack(){
		for(int i = 0; i < index; i++){
			System.out.println(obj[i]);
		}
	}
	
	public static void main(String[] args) {
		Stack s = new Stack();
		int i = 1;
		int j = 2;
		s.push(i);
		s.push(j);
		System.out.println(s.getPop());
		s.printStack();
	}
}