Java实现泛型Stack-CPT102-Lab5

主要的难点在于：

　　1. 泛型的使用

　　2. 内存的动态开辟

　　3. 深度拷贝与浅拷贝的区别（line 30）

package xxx.xxxxxxx;

import java.util.EmptyStackException;

public class ArrayStack<E> implements Cloneable {

    private E[] data;
    private int manyItems;

    public ArrayStack() {
        final int INITIAL_CAPACITY = 10;
        manyItems = 0;
        data = (E[]) new Object[INITIAL_CAPACITY];
    }

    public ArrayStack(int initialCapacity) {
        if (initialCapacity < 0)
            throw new IllegalArgumentException("initialCapacity is negative: " + initialCapacity);
        manyItems = 0;
        data = (E[]) new Object[initialCapacity];
    }

    public ArrayStack<E> clone() {
        ArrayStack<E> copy;
        try {
            copy = (ArrayStack<E>) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new RuntimeException("This class does not implement Cloneable");
        }
        copy.data = data.clone();
        return copy;
    }

    public void ensureCapacity(int minimumCapacity) {
        E biggerArray[];
        if (data.length < minimumCapacity) {
            biggerArray = (E[]) new Object[minimumCapacity];
            System.arraycopy(data, 0, biggerArray, 0, manyItems);
            data = biggerArray;
        }
    }

    public int getCapacity() {
        return data.length;
    }

    public boolean isEmpty() {
        return manyItems == 0;
    }

    public E peek() {
        if (manyItems == 0)
            throw new EmptyStackException();
        return data[manyItems - 1];
    }

    public E pop() {
        if (manyItems == 0)
            throw new EmptyStackException();
        return data[--manyItems];
    }

    public void push(E e) {
        if (manyItems == data.length)
            ensureCapacity(manyItems * 2 + 1);
        data[manyItems++] = e;
    }

    public int size() {
        return manyItems;
    }

    public void trimToSize() {
        E trimmedArray[];
        if (data.length != manyItems) {
            trimmedArray = (E[]) new Object[manyItems];
            System.arraycopy(data, 0, trimmedArray, 0, manyItems);
            data = trimmedArray;
        }
    }

    public int remainedCapacity() {
        return data.length - manyItems;
    }
}