题目：
数据结构——使用数组实现栈
自己实现一个栈，要求这个栈具有push()、pop()（返回栈顶元素并出栈）、peek() （返回栈顶元素不出栈）、isEmpty()、size()这些基本的方法。
import java.util.Arrays;
/**
* @Name:
* @Description: 使用数组实现栈:自己实现一个栈，要求这个栈具有push()、pop()（返回栈顶元素并出栈）、peek() （返回栈顶元素不出栈）、isEmpty()、size()这些基本的方法。
* @Author:hutao2@myhexin.com
* @Date:2019/10/31 13:49
*/
public class Mystack {
private int[] storage;//存放栈中元素的数组
private int capacity;//栈的容量
private int count;//栈中元素数量
private static final int GROW_FACTOR = 2;
//不带初始容量的构造方法。默认容量为8
public Mystack(){
this.capacity = 8;
this.storage = new int[8];
this.count = 0;
}
//带初始容量的构造方法
public Mystack(int initialCapacity){
if(initialCapacity < 1)
throw new IllegalArgumentException("Capacity too small");
this.capacity = initialCapacity;
this.storage = new int[initialCapacity];
this.count = 0;
}
//确保容量大小
private void ensureCapacity(){
int newCapacity = capacity * GROW_FACTOR;
storage = Arrays.copyOf(storage,newCapacity);
capacity = newCapacity;
}
//入栈
public void push(int value){
if(count == capacity){
ensureCapacity();
}
storage[count++] = value;
}
//返回栈顶元素并出栈
private int pop(){
count--;
if (count == -1)
throw new IllegalArgumentException("Stack is empty");
return storage[count];
}
//返回栈顶元素并出栈
private int peek(){
if(count == 0){
throw new IllegalArgumentException("Stack is empty");
}else{
return storage[count-1];
}
}
//判断是否为空
private boolean isEmpty(){
return count == 0;
}
//返回栈中元素的个数
private int size(){
return count;
}
public static void main(String[] args) {
Mystack mystack = new Mystack(3);
mystack.push(1);
mystack.push(2);
mystack.push(3);
mystack.push(4);
mystack.push(5);
mystack.push(6);
mystack.push(7);
mystack.push(8);
System.out.println(mystack.peek());//8
System.out.println(mystack.size());//8
for (int i = 0; i < 8; i++) {
System.out.println(mystack.pop());
}
System.out.println(mystack.isEmpty());//true
mystack.pop();//报错：java.lang.IllegalArgumentException: Stack is empty.
}
}
