中缀到后缀表达式解析（带有 Swing 实现的 JAVA）

Question

I was tasked to Create a JAVA Swing GUI Program implementation that will output the Infix to Postfix and Infix to Prefix Notation Conversion, as well as how the conversion takes place via The Expression Parsing of the Prefix Stack and Operator Stack one by one. in this case I used a JTable to output the Expression Parsing along with the Scanned Infix Notation Operators and Operands.

The Problem: I am having a hard time creating the logic in outputing the Prefix stack and the Operator stack in the JTable. Seen in the Picture Below: Table 1.1

This is the objective we were tasked to create: Table 1.2

Same goes to the Infix to Prefix Notation Conversion: Table 1.3

Anyone have any Ideas other than what I Created in Table 1.1?

Infix to Postfix Code:

public static int precedence(char o){
    switch(o){
        case '+':
        case '-':
            return 1;
        case '*':
        case '/':
            return 2;
        case '^':
            return 3;
    }
    return -1;
}

public String infixToPostfix(String expression){
    String result = "";
    Stack<Character> stack = new Stack<>();
    for (int i = 0; i < expression.length(); i++){
        char o = expression.charAt(i);
        if(precedence(o) > 0){
            while(stack.isEmpty() == false && precedence(stack.peek()) >= precedence(o)){
                result += stack.pop();
            }
            stack.push(o);

        }else if(o==')'){
            char x = stack.pop();
            while(x!='('){
                result += x;
                x = stack.pop();
            }
            
        }else if(o=='('){
            result += o;
            
        }else{
            result += o;
        }
    }
    for (int i =0; i <= stack.size(); i++){
        result += stack.pop();
    }
    return result;
}

Enter JButton Code:

private void EnterButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                             
    
    // ENTER BUTTON FUNCTION

    String expression = InfixInput1.getText(); 
    if(expression.isEmpty()){
        DisplayInput1.setText("NOTHING TO CONVERT!");
    }else{
        System.out.println("POSTFIX CONVERSION : "+infixToPostfix(expression));
        DisplayInput1.setText(expression);
        PostfixOutput.setText(infixToPostfix(expression));
    }
    PostfixTable.getColumnModel().getColumn(0).setPreferredWidth(5);
    PostfixTable.getColumnModel().getColumn(1).setPreferredWidth(5);
    PostfixTable.getColumnModel().getColumn(2).setPreferredWidth(5);

    String header[] = {"Scanned Symbol","Postfix Stack", "Operator Stack"};
    PostfixTable.setAutoCreateColumnsFromModel(true);
    TableColumn column1 = PostfixTable.getTableHeader().getColumnModel().getColumn(0);
    column1.setHeaderValue(header[0]);

    TableColumn column2 = PostfixTable.getTableHeader().getColumnModel().getColumn(1);
    column2.setHeaderValue(header[1]);

    TableColumn column3 = PostfixTable.getTableHeader().getColumnModel().getColumn(2);
    column3.setHeaderValue(header[2]);
    
    for(int i = 0; i <= expression.length()-1; i++){
        char a = expression.charAt(i);
        DefaultTableModel model = (DefaultTableModel) PostfixTable.getModel();
        model.addRow(new Object[]{a});
    }
}                   

Answer 1

I went ahead and created a bare-bones basic Swing GUI to replicate your GUI.

Here's what the GUI looks like.

The code you need to work on is located in the infixToPostfix method of the ConversionListener class. I don't understand your conversion code well enough to put the call to the insertRow method in all the correct places.

Here's the complete runnable code. I made the additional classes inner classes so I could post the code as one block.

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;

public class InfixToPostfixGUI implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new InfixToPostfixGUI());
    }
    
    private final InfixToPostfixModel model;
    
    private JTextField infixField, postfixField;
    
    public InfixToPostfixGUI() {
        this.model = new InfixToPostfixModel();
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Infix to postfix parsing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        frame.add(createDisplayPanel(), BorderLayout.CENTER);
        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
    
    private JPanel createDisplayPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        
        panel.add(createInfixPanel(), BorderLayout.NORTH);
        panel.add(createTablePanel(), BorderLayout.CENTER);
        panel.add(createPostfixPanel(), BorderLayout.SOUTH);
        
        return panel;
    }
    
    private JPanel createInfixPanel() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        JLabel label = new JLabel("Infix Expression:");
        panel.add(label);
        
        infixField = new JTextField(30);
        panel.add(infixField);
        
        JButton button = new JButton("Enter");
        button.addActionListener(new ConversionListener(this, model));
        panel.add(button);
        
        return panel;
    }
    
    private JPanel createTablePanel() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        JTable table = new JTable(model.getTableModel());
        JScrollPane scrollPane = new JScrollPane(table);
        panel.add(scrollPane);
        
        return panel;
    }
    
    private JPanel createPostfixPanel() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        JLabel label = new JLabel("Postfix Expression:");
        panel.add(label);
        
        postfixField = new JTextField(30);
        postfixField.setEditable(false);
        panel.add(postfixField);
        
        return panel;
    }
    
    public String getInfixExpression() {
        return infixField.getText().trim();
    }
    
    public void setPostfixExpression() {
        postfixField.setText(model.getPostfixExpression());
    }
    
    public class ConversionListener implements ActionListener {
        
        private final InfixToPostfixGUI view;
        
        private final InfixToPostfixModel model;

        public ConversionListener(InfixToPostfixGUI view, InfixToPostfixModel model) {
            this.view = view;
            this.model = model;
        }

        @Override
        public void actionPerformed(ActionEvent event) {
            String infixExpression = view.getInfixExpression();
            model.setInfixExpression(infixExpression);
            model.setPostfixExpression(infixToPostfix(infixExpression));
            view.setPostfixExpression();
        }
        
        private String infixToPostfix(String expression) {
            removeAllRows(model.getTableModel());
            String result = "";
            Stack<Character> stack = new Stack<>();

            for (int i = 0; i < expression.length(); i++) {
                char o = expression.charAt(i);
                if (precedence(o) > 0) {
                    while (!stack.isEmpty() && precedence(stack.peek()) >= precedence(o)) {
                        String token = Character.toString(stack.pop());
                        insertRow(model.getTableModel(), token, "", "", "", "");
                        result += token;
                    }
                    stack.push(o);

                } else if (o == ')') {
                    char x = stack.pop();
                    while (x != '(') {
                        result += x;
                        x = stack.pop();
                    }

                } else if (o == '(') {
                    String token = Character.toString(o);
                    insertRow(model.getTableModel(), token, "", "", "", "");
                    result += token;

                } else {
                    String token = Character.toString(o);
                    insertRow(model.getTableModel(), token, "", "", "", "");
                    result += token;
                }
            }

            for (int i = 0; i <= stack.size(); i++) {
                String token = Character.toString(stack.pop());
                insertRow(model.getTableModel(), token, "", "", "", "");
                result += token;
            }

            return result;
        }
        
        private int precedence(char o) {
            switch (o) {
            case '+':
            case '-':
                return 1;
            case '*':
            case '/':
                return 2;
            case '^':
                return 3;
            default:
                return -1;
            }
        }
        
        private void removeAllRows(DefaultTableModel tableModel) {
            int size = tableModel.getRowCount();
            for (int index = 0; index < size; index++) {
                tableModel.removeRow(0);
            }
        }
        
        private void insertRow(DefaultTableModel tableModel, String token, 
                String action, String result, String stack, String notes) {
            Object[] object = new Object[5];
            object[0] = token;
            object[1] = action;
            object[2] = result;
            object[3] = stack;
            object[4] = notes;
            tableModel.addRow(object);
        }
        
    }
    
    public class InfixToPostfixModel {
        
        private final DefaultTableModel tableModel;
        
        private String infixExpression, postfixExpression;
        
        public InfixToPostfixModel() {
            tableModel = new DefaultTableModel();
            tableModel.addColumn("Token");
            tableModel.addColumn("Action");
            tableModel.addColumn("Result");
            tableModel.addColumn("Stack");
            tableModel.addColumn("Notes");
        }

        public DefaultTableModel getTableModel() {
            return tableModel;
        }

        public String getInfixExpression() {
            return infixExpression;
        }

        public void setInfixExpression(String infixExpression) {
            this.infixExpression = infixExpression;
        }

        public void setPostfixExpression(String postfixExpression) {
            this.postfixExpression = postfixExpression;
        }

        public String getPostfixExpression() {
            return postfixExpression;
        }
        
    }

}