package Stack;

/*
 @author: Roderland
 @create: 2020年08月10日---21:12
*/
/*
 自编数组实现简单栈
 */
public class MyArrayStack<E> {

 private static final int DEFAULT_CAPACITY = 10;

 private E[] array;

 private int elementCount = 0;

 public MyArrayStack(int capacity) { array = (E[])new Object[capacity]; }

 public MyArrayStack() { array = (E[])new Object[DEFAULT_CAPACITY]; }

 public void push(E o) {
 if (elementCount >= array.length) expansion();
 array[elementCount++] = o;
 }

 private void expansion() {
 E[] newArray = (E[]) new Object[array.length*2];
 //System.arraycopy(array, 0, newArray, 0, array.length);
 for (int i = 0; i < array.length; i++) {
 newArray[i] = array[i];
 }
 array = newArray;
 }

 public E peek() {
 EmptyCheck();
 return array[elementCount-1];
 }

 public E pop() {
 EmptyCheck();
 return array[--elementCount];
 }

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

 public int size() {
 return elementCount;
 }

 private void EmptyCheck() {
 if (isEmpty())
 throw new IndexOutOfBoundsException("栈空");
 }

}