生长堆

package com.company.stucts.stack;


import java.util.Arrays;
// 来 自 NowJava.com - 时  代  Java

public class GrowingStack {

    private Object[] data;

    private int top;


    public GrowingStack(int size) {

        if (size < 0) {

            throw new IllegalStateException("Stack size negative value!");

        }

        data = new Object[size];

        top = 0;
        /**
         * nowjava.com - 时代Java 提 供 
        **/

    }


    public void push(Object o) {

        ensureCapacity();

        data[top++] = o;

    }


    public Object pop() {

        if (top == 0) {

            throw new IllegalStateException("Stack is empty");

        }

        Object o = data[--top];

        data[top] = null;

        return o;

    }


    public boolean isEmpty() {

        return top != 0;

    }


    private void ensureCapacity() {

        if (top == data.length) {

            int oldSize = data.length;

            int newSize = oldSize * 2 + 1;

            System.out.println("Stack is grow! Old size: " + oldSize

                    + ", new size: " + newSize);

            data = Arrays.copyOf(data, newSize);

        }

    }


    @Override

    public String toString() {

        return "Queue: " + "\n" + "data[]: " + Arrays.toString(data) + "\n"

                + "data[] length: " + data.length + "\n" + "top: " + top;

    }