Question

我正在尝试编写一个程序，它将利用堆栈来检查是否存在左括号/括号在用户的输入中具有重合的右括号/括号。虽然我已经大力搜索了代码，但我似乎无法找到我做错的事情。以下代码块是方法＆＃34;检查＆＃34;我试图实施。

import java.util.Stack;
public class Matching {

public static int checking(String s) {

    Stack<String> stack = new Stack<>();

    for (int i = 0; i < s.length(); i++) {
        if (s.substring(i, i + 1).equals("{") || s.substring(i, i + 1).equals("}")){ //if substring is a bracket

            if (s.substring(i, i + 1).equals("{"))  //if is left bracket push onto stack
                stack.push("{");

            else if (!stack.peek().equals("{") || stack.size() <= 0) //otherwise, check if left bracket is not at top or if stack is empty
                return 3; // "right brace does not have its matching left brace"

            else if (s.substring(i, i + 1).equals("}") && stack.peek().equals("{"))//otherwise if substring is a right brace and the top is a left brace
                stack.pop(); //remove from top, continue searching
        }

        if (s.substring(i, i + 1).equals("{") || s.substring(i, i + 1).equals("}")){ //if substring is a parenthesis

            if (s.substring(i, i + 1).equals("(")) // if is left parenthesis push onto stack
                stack.push("(");

            else if (!stack.peek().equals("(") || stack.size() <= 0) //otherwise, check if left parenthesis is not at top or if stack is empty
                return 1;

            else if (s.substring(i).equals(")") && stack.peek().equals("(")) //otherwise if substring is a right parenthesis and the top is a left parenthesis
                stack.pop(); //remove from top, continue searching
        }

        if (stack.size() == 0) //
            return 0;
        else if (stack.size() != 0 && stack.peek().equals("("))
            return 2;
        else if (stack.size() != 0 && stack.peek().equals("{"))
            return 4;
    }
    return 150; //checks for error
  }
 }

我的问题是程序输出所有内容都匹配（返回0），无论情况如何。这是我的主要方法：

import java.io.*;

public class Assignment11
{
    public static void main (String[] args) throws IOException
    {
        char input1;
        String inputInfo;
        String line = new String();

    printMenu();

    InputStreamReader isr = new InputStreamReader(System.in);
    BufferedReader stdin = new BufferedReader(isr);

    do  // will ask for user input
    {
        System.out.println("What action would you like to perform?");
        line = stdin.readLine();
        input1 = line.charAt(0);
        input1 = Character.toUpperCase(input1);

        if (line.length() == 1)
        {
            // matches one of the case statements
            switch (input1)
            {
                case 'P':   //Enter String
                    System.out.print("Please enter a string.\n");
                    inputInfo = stdin.readLine().trim();
                    int result = Matching.checking(inputInfo);
                    if (result == 0)
                        System.out.println("Everything is matching");
                    else if (result == 1)
                        System.out.println("right parenthesis does not have its matching left parenthesis");
                    else if (result == 2)
                        System.out.println("left parenthesis does not have its matching right parenthesis");
                    else if (result == 3)
                        System.out.println("right brace does not have its matching left brace");
                    else if (result == 4)
                        System.out.println("left brace does not have its matching right brace");
                    break;
                case 'Q':   //Quit
                    break;
                case '?':   //Display Menu
                    printMenu();
                    break;
                default:
                    System.out.print("Unknown action\n");
                    break;
            }
        }
        else
        {
            System.out.print("Unknown action\n");
        }
    } while (input1 != 'Q' || line.length() != 1);
}


/** The method printMenu displays the menu to a user**/
public static void printMenu()
{
    System.out.print("Choice\t\tAction\n" +
            "------\t\t------\n" +
            "P\t\tEnter String\n" +
            "Q\t\tQuit\n" +
            "?\t\tDisplay Help\n\n");
}

}

非常感谢任何帮助或一般指示！

Answer 1

查看您的第二个if声明：

if (s.substring(i, i + 1).equals("{") || s.substring(i, i + 1).equals("}")){ //if substring is a parenthesis

评论表示它正在检查左右parens，但代码表示......

堆栈程序的运行时错误

1 个答案: