為什么我的 stack.size() 方法不起作用？

Question

import java.util.Scanner;
import java.util.*;
/**
 * Write a description of class RPN here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
public class RPN
{
    // instance variables - replace the example below with your own
    private Stack stack;
    private Menu menu;

    /**
     * Constructor for objects of class RPN
     */
    public RPN()
    {
        // initialise instance variables
        stack = new Stack();
        menu = new Menu();
    }

    public boolean isInteger(String ytemp) 
    {
    //for (int i = 0; i<ytemp.length; i++)
    //{
        try 
        {
            Integer.parseInt(ytemp);
            return true;
        }
        catch( Exception e ) 
        {
            return false;
        }
    }

    /**
     * An example of a method - replace this comment with your own
     *
     * @param  y  a sample parameter for a method
     * @return    the sum of x and y
     */
    public String[] processString()
    {   
        stack.initialiseStack();
        String[] temp;
        String delimiter = ",";
        System.out.println("Please input a combination of integers and operators, separated by a comma but no spaces (e.g. 3,9,2,+,5,*,-)");
        Scanner s = new Scanner(System.in);
        String string = s.nextLine();
        temp = string.split(delimiter);
        return temp;
    }
    
    public void validateString(String[] xtemp)
    {
        for (int i = 0; i<xtemp.length; i++)
        {
            try
            {
                if(xtemp[i].equals("+"))
                {
                    int a = stack.pop();
                    int b = stack.pop();
                    int c = b + a;
                    stack.push(c);
                }
                else if(xtemp[i].equals("-"))
                {
                    int a = stack.pop();
                    int b = stack.pop();
                    int c = b - a;
                    stack.push(c);
                }
                else if(xtemp[i].equals("*"))
                {
                    int a = stack.pop();
                    int b = stack.pop();
                    int c = b * a;
                    stack.push(c);
                }
                else if(xtemp[i].equals("/"))
                {
                    int a = stack.pop();
                    int b = stack.pop();
                    int c = b / a;
                    stack.push(c);
                }
                else if(isInteger(xtemp[i]) == true)
                {
                    int n = Integer.parseInt(xtemp[i]);
                    stack.push(n);
                }
                else
                {
                   System.out.println("invalid input. Please ensure that your input solely consists of integers and the 4 main operators (+, -, *, /) separated by a comma. an example of a valid input would be the following: 4,7,+,2,*");
                   validateString(processString());
                }
            }
            catch (EmptyStackException e)
            {
                System.out.println("Error identified: " + e.getErrorMessage());
            }
        }
        if (stack.size() == 1)
        {
        stack.printStack();
    }
}
}

如果最后的堆棧大小不是 1，我希望我的代碼給出錯誤。為什么它無法識別 stack.size 方法？ 這不是 Java.util.* 的一部分嗎？ 你認為這是因為我已經有一個堆棧 class 所以它與它混淆了嗎？ 抱歉，如果這是一個奇怪的問題，但我真的需要幫助...................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................

Answer 1

java.util.Stack沒有size()方法。 它有empty()方法。

嘗試使用empty()方法來解決您的問題。