（JAVA）中缀到postfix的转换和计算

Question

我正在使用中缀来进行后缀计算。我想出了main.java的GUI，用于将输入中缀转换为postfix和calculate的Evaluation.java，以及除以0的DivisionException.java。但是，程序本身工作正常，但计算，检查括号对和DivisionException是不正常。我甚至无法判断我是否正确编写了ActionListener方法。请帮我一把。

// Main.java

    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
    import java.io.*;
    import java.util.*;

    public class Main extends JFrame{
private GridLayout glm = new GridLayout(3, 1, 5, 20);
private JPanel jp1 = new JPanel();
private JPanel jp2 = new JPanel();
private JPanel jp3 = new JPanel();
private GridLayout gl1 = new GridLayout (1, 2);
private JLabel jl1 = new JLabel("Enter Infix Expression", JLabel.CENTER);
private JTextField jtf1 = new JTextField();
private GridLayout gl2 = new GridLayout(1, 3, 5, 9);
private JButton jbEvaluate = new JButton("Evaluate");
private GridLayout gl3 = new GridLayout(1, 2);
private JLabel jl2 = new JLabel("Result", JLabel.CENTER);
private JTextField jtf2 = new JTextField();
private String postfixExpression;
private int result;

public String userInput(){
    return (String)jtf1.getText();
}

public Main(){
    setTitle("Infix Expression Evaluator");
    setSize(500, 200);
    setLayout(glm);
    jp1.setLayout(gl1);
    jp1.add(jl1);
    jp1.add(jtf1);
    add(jp1);
    jp2.setLayout(gl2);
    jp2.add(new JLabel(""));
    jp2.add(jbEvaluate);
    jbEvaluate.addActionListener(new EnterActionListener());
    jp2.add(new JLabel(""));
    add(jp2);
    jp3.setLayout(gl3);
    jp3.add(jl2);
    jp3.add(jtf2);
    jtf2.setEditable(false);
    jtf2.setBackground(Color.lightGray);
    add(jp3);
    setLocationRelativeTo(null);
    setResizable(true);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

class EnterActionListener implements ActionListener{
    public void actionPerformed(ActionEvent ae){
        try{
            if(userInput() == null){
                JOptionPane.showMessageDialog(null, "Paranthesis does not match", "Paranthesis Error", JOptionPane.WARNING_MESSAGE);    
                }
            else if(Evaluation.checkParenthesis(userInput()) == true){
            postfixExpression = Evaluation.InfixToPostfix(userInput());
            result = Evaluation.Calculation(postfixExpression);
            jtf2.setText(Integer.toString(result));
                }
            else if(Evaluation.checkParenthesis(userInput()) == false){
                JOptionPane.showMessageDialog(null, "Paranthesis does not match", "Paranthesis Error", JOptionPane.WARNING_MESSAGE);
                }
            else if(userInput() == null){
                JOptionPane.showMessageDialog(null, "Paranthesis does not match", "Paranthesis Error", JOptionPane.WARNING_MESSAGE);    
                }
            }catch(DivisionException de){
                new DivisionException();
            }
        }
    }

public static void main (String[] args){
    Main main = new Main();
    }
}

// Evaluation.java

import java.util.*;
import javax.swing.JOptionPane;
public class Evaluation {

 public static String InfixToPostfix(String infixExpression){

    boolean numberEnd = false;
    String postfixExpression = "";
    Stack stack = new Stack();

    for(int i = 0; i< infixExpression.length(); i++){
        char infixExpChar = infixExpression.charAt(i);
        switch(infixExpChar){
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            postfixExpression = postfixExpression.concat(infixExpChar+"");
            numberEnd = true;
            break;
        case ' ':
            JOptionPane.showMessageDialog(null, "Space in between expression is unacceptable", "Spacing Error", JOptionPane.WARNING_MESSAGE);
            break;
        case '(':
            if(numberEnd == true){
                postfixExpression = postfixExpression.concat(" ");
                numberEnd = false;
            }else{
            stack.push(new Character('('));
            break;
            }
        case ')':
            if(numberEnd == true){
                postfixExpression = postfixExpression.concat(" ");
                numberEnd = false;
            }else{
                while(((Character)stack.peek()).charValue() != '('){
                    postfixExpression = postfixExpression.concat(((Character)stack.pop()).toString());
                }
            }Object openParenthesis = stack.pop();
            break;
        case '+':
        case '-':
        case '*':
        case '/':
            if(numberEnd == true){
                postfixExpression = postfixExpression.concat(" ");
                numberEnd = false;
            }
            while(!stack.isEmpty() && (((Character) stack.peek()).charValue()) != '(' && (Precedence(infixExpChar)) <= Precedence(((Character)stack.peek()).charValue())){
                postfixExpression = postfixExpression.concat(((Character)stack.pop()).toString());
            }
            stack.push(new Character(infixExpChar));
            break;
        }
    }if(numberEnd == true){
        postfixExpression = postfixExpression.concat(" ");
        numberEnd = false;
    }while(!stack.isEmpty()){
        postfixExpression = postfixExpression.concat(((Character)stack.pop()).toString());
    }
    return postfixExpression;
}

public static int Calculation(String postfixExpression) throws DivisionException{

    int value1, value2;
    String temporary = "";
    Stack stack = new Stack();

    for(int i = 0; i < postfixExpression.length(); i++){
        char postfixExpChar = postfixExpression.charAt(i);
        switch(postfixExpChar){
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                temporary = temporary.concat(postfixExpChar+"");
                break;
            case ' ':
                stack.push(new Integer(temporary));
                temporary = new String();
                break;
            case '+':
                value1 = new Integer(((Integer)stack.pop()).intValue() + ((Integer)stack.pop()).intValue());
                stack.push(value1);
                break;
            case '-':
                value2 = new Integer(((Integer)stack.pop()).intValue());
                value1 = new Integer(((Integer)stack.pop()).intValue() - value2);
                stack.push(value1);
                break;
            case '*':
                value1 = new Integer(((Integer)stack.pop()).intValue() * ((Integer)stack.pop()).intValue());
                stack.push(value1);
                break;
            case '/':
                value2 = new Integer(((Integer)stack.pop()).intValue());
                value1 = new Integer(((Integer)stack.pop()).intValue() / value2);
                    if(value2 == 0){
                        throw new DivisionException();
                    }
                stack.push(value1);
                break;
        }
    }return (int) stack.peek();
}

public static int Precedence(char operator){
    int precedence = 0;
    switch(operator){
        case '+':
        case '-':
            precedence = 1;
            break;
        case '*':
        case '/':
            precedence = 2;
            break;
    }return precedence;
}

public static boolean checkParenthesis(String exp){
    Stack stack = new Stack();
    for (int i = 0; i < exp.length(); i++){
        char character = exp.charAt(i);
        if(character == '('){
            stack.push(new Character(character));
        }else if(character == ')'){
            if(stack.isEmpty()){
                JOptionPane.showMessageDialog(null, "Parenthesis does not match", "Parenthesis Error", JOptionPane.WARNING_MESSAGE);
                return false;
            }else 
                return true;
        }
    }return stack.isEmpty();
}
}

// DivisionException

import javax.swing.JOptionPane;
public class DivisionException extends Exception{
    public DivisionException(){
        JOptionPane.showMessageDialog(null, "Cannot divide a number by 0", "Division Error", JOptionPane.WARNING_MESSAGE);
    }
    }