package com.coding.basic;
import java.util.EmptyStackException;
public class Stack {
private Object[] elementData;
private int size;
public Stack() {
this.size = 0;
this.elementData = new Object[10];
}
public void push(Object o) {
if (o == null)
throw new RuntimeException("元素不可为NULL");
size++;
elementData[size -1]= o ;
}
public Object pop() {
if (isEmpty())
throw new EmptyStackException();
Object old = elementData[size - 1];
elementData[size] = null;
size--;
return old;
}
public Object peek() {
if (isEmpty())
throw new EmptyStackException();
return elementData[size -1];
}
public boolean isEmpty() {
return size < 1;
}
//
public int size() {
return size;
}
}