java 实现下压栈的操作(能动态调整数组大小)

import java.util.Iterator;

public class ResizingArrayStack<Item> implements Iterable<Item>

{

   private Item[] a=(Item[]) new Object[ 1 ];

   private int N= 0 ;

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

   public int size() { return N;}

   private void resize( int max)

   {

     Item[] temp=(Item[]) new Object[max];

     for ( int i= 0 ; i<N; i++)

     {

       temp[i]=a[i];

     }

     a=temp;

   }

   public void push(Item item)

   {

     if (N==a.length) resize( 2 *a.length);

     a[N++]=item;

   }

   public Item pop()

   {

     Item item=a[--N];

     a[N]= null ;

     if (N> 0 && N==a.length/ 4 ) resize(a.length/ 2 );

     return item;

   }

   public Iterator<Item> iterator()

   { return new ReverseArrayIterator();}

   private class ReverseArrayItertor implements Iterator<Item>

   {

     private int i=N;

     public boolean hasNext() { return i> 0 ;}

     public Item next() { return a[--i];}

     public void remove() {}

   }

}

package com.atguigu.stack;

import java.util.Scanner;

public class ArrayStackDemo {

  public static void main(String[] args) {

  //测试

  ArrayStack stack = new ArrayStack( 4 );

  String key= "" ;

  boolean loop = true ;

  Scanner scanner = new Scanner(System.in);

  while (loop) {

   System.out.println( "show:表示显示栈" );

   System.out.println( "exit:退出程序" );

   System.out.println( "push:表示添加数据到栈（入栈）" );

   System.out.println( "pop:表示从栈取出数据（出栈）" );

   System.out.println( "请输入你的选择" );

   key = scanner.next();

   switch (key) {

   case "show" :

   stack.list();

   break ;

   case "push" :

   System.out.println( "请输入一个数" );

   int value = scanner.nextInt();

   stack.push(value);

   break ;

   case "pop" :

   try {

    int res = stack.pop();

    System.out.printf( "出栈的语句是%d\n" , res);

   } catch (Exception e) {

    System.out.println(e.getMessage());

   }

   break ;

   case "exit" :

   scanner.close();

   loop = false ;

   break ;

   default :

    break ;

   }

  }

  System.out.println( "程序退出" );

  }

}

class ArrayStack{

  private int maxSize;

  private int [] stack;

  private int top = - 1 ;

  public ArrayStack( int maxSize) {

  this .maxSize=maxSize;

  stack = new int [ this .maxSize];

  }

   //栈满

  public boolean isFull() {

  return top == maxSize - 1 ;

  }

   //栈空

  public boolean isEmpty() {

  return top == - 1 ;

  }

  //出栈

  public void push( int value) {

  if (isFull()) {

   System.out.println( "栈满" );

  }

  top++;

  stack[top] =value;

  }

  //出栈

  public int pop() {

  if (isEmpty()) {

   throw new RuntimeException( "栈空" );

  }

  int value = stack[top];

  top--;

  return value;

  }

  //遍历栈

  public void list() {

  if (isEmpty()) {

   System.out.println( "栈空，没有数据" );

   return ;

  }

  for ( int i = top;i>= 0 ;i--) {

   System.out.printf( "stack[%d]=%d\n" ,i,stack[i]);

  }

  }

}