使用pop（）和push（）的堆栈数组

Question

我为使用堆栈的程序创建的2个类有问题。我得到的第一个问题是，当我尝试运行程序时，出现运行时错误。

这很难问，因为它做了很多事情。它要求用户输入以将数字添加到堆栈中，并检查堆栈是满还是空。我也可能需要帮助来复制阵列。

线程“主”中的异常java.lang.ArrayIndexOutOfBoundsException：在Lab15.main（Lab15.java:38）处在IntegerStack.push（IntegerStack.java:24）处为-1

这是运行程序的主要类。

import java.util.Scanner;


public class Lab15 {

    public static void main(String[] args)
    {
        System.out.println("***** Playing with an Integer Stack *****");
        final int SIZE = 5;
        IntegerStack myStack = new IntegerStack(SIZE);
        Scanner scan = new Scanner(System.in);

        //Pushing integers onto the stack
        System.out.println("Please enter an integer to push onto the stack - OR - 'q' to Quit");
        while(scan.hasNextInt())
        {
            int i = scan.nextInt();
            myStack.push(i);
            System.out.println("Pushed "+ i);
        }

        //Pop a couple of entries from the stack
        System.out.println("Lets pop 2 elements from the stack");
        int count = 0;
        while(!myStack.isEmpty() && count<2)
        {
            System.out.println("Popped "+myStack.pop());
            count++;
        }

        scan.next(); //Clearing the Scanner to get it ready for  further input.

        //Push a few more integers onto the stack
        System.out.println("Push in a few more elements - OR - enter q to quit");
        while(scan.hasNextInt())
        {
            int i = scan.nextInt();
            myStack.push(i);
            System.out.println("Pushed "+ i);
        }

        System.out.println("\nThe final contentes of the stack are:");
        while(!myStack.isEmpty())
        {
            System.out.println("Popped "+myStack.pop());
        }

    }

}

这是将数字加到堆栈上的类，这就是问题所在。这是我可能需要复制阵列的帮助。在末尾。

import java.util.Arrays;

public class IntegerStack 
{
    private int stack [];
    private int top;

    public IntegerStack(int SIZE) 
    {
        stack = new int [SIZE];
        top = -1;
    }

    public void push(int i) 
    {
        if (top == stack.length)
        {
            extendStack();
        }

        stack[top]= i;
        top++;
    }

    public int pop() 
    {
        top --;
        return stack[top];
    }

    public int peek()
    {
        return stack[top];
    }

    public boolean isEmpty() 
    {
        if ( top == -1);
        {
            return true;
        }
    }

    private void extendStack()
    {
        int [] copy = Arrays.copyOf(stack, stack.length);
    }
}

任何帮助或指示，将不胜感激。

Answer 1

为您的Stack实施提供更好的解决方案

import java.util.List;
import java.util.ArrayList;
public class IntegerStack

{

    private List<Integer> stack;

    public IntegerStack(int SIZE) 
    {
        stack = new ArrayList<Integer>(SIZE);
    }

    public void push(int i) 
    {

       stack.add(0,i);
     }

     public int pop() 
     { 
        if(!stack.isEmpty()){
           int i= stack.get(0);
           stack.remove(0);
           return i;
        } else{
           return -1;// Or any invalid value
        }
     }

     public int peek()
     {
        if(!stack.isEmpty()){
           return stack.get(0);
        } else{
           return -1;// Or any invalid value
        }
     }


     public boolean isEmpty() 
     {
       stack.isEmpty();
     }

 }

如果您必须使用Array …这是您的代码中的问题以及可能的解决方案

import java.util.Arrays;
public class IntegerStack 
{

    private int stack [];
    private int top;

    public IntegerStack(int SIZE) 
   {
    stack = new int [SIZE];
    top = -1; // top should be 0. If you keep it as -1, problems will arise when SIZE is passed as 0. 
    // In your push method -1==0 will be false and your code will try to add the invalid element to Stack .. 
     /**Solution top=0; */
    }

public void push(int i) 
{
    if (top == stack.length)
    {
        extendStack();
    }

       stack[top]= i;
        top++;

}

public int pop() 
{
    top --; // here you are reducing the top before giving the Object back 
   /*Solution 
      if(!isEmpty()){
      int value = stack[top];
       top --;
     return value; 
    } else{
      return -1;// OR invalid value
    }
   */
    return stack[top];
}

public int peek()
{
    return stack[top]; // Problem when stack is empty or size is 0
    /*Solution 
       if(!isEmpty()){
         return stack[top];
       }else{
         return -1;// Or any invalid value
       }
    */


}


public boolean isEmpty() 
{
    if ( top == -1); // problem... we changed top to 0 above so here it need to check if its 0 and there should be no semicolon after the if statement
   /* Solution if(top==0) */
    {
        return true;
    }
}

private void extendStack()
{

    int [] copy = Arrays.copyOf(stack, stack.length); // The second parameter in Arrays.copyOf has no changes, so there will be no change in array length.
  /*Solution  
    stack=Arrays.copyOf(stack, stack.length+1); 
   */
     }

     }