基于 Java Swing 的个人所得税计算模拟器源码

2. 个税计算核心类

package com.tax.calculator;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.HashMap;
import java.util.Map;

/**
 * 个人所得税计算器
 * 实现 2023 年最新个税计算规则
 */
public class TaxCalculator {  
    
    // 税率表（年度综合所得）
    private static final TaxBracket[] TAX_BRACKETS = {
        new TaxBracket(0, 36000, 0.03, 0),
        new TaxBracket(36000, 144000, 0.10, 2520),
        new TaxBracket(144000, 300000, 0.20, 16920),
        new TaxBracket(300000, 420000, 0.25, 31920),
        new TaxBracket(420000, 660000, 0.30, 52920),
        new TaxBracket(660000, 960000, 0.35, 85920),
        new TaxBracket(960000, Double.MAX_VALUE, 0.45, 181920)
    };  
    
    // 月度专项扣除标准
    private static final Map<String, BigDecimal> SPECIAL_DEDUCTIONS = new HashMap<>();  
    
    static {
        // 初始化专项扣除标准（月度）
        SPECIAL_DEDUCTIONS.put("养老", new BigDecimal("1000"));
        SPECIAL_DEDUCTIONS.put("医疗", new BigDecimal("200"));
        SPECIAL_DEDUCTIONS.put("失业", new BigDecimal("50"));
        SPECIAL_DEDUCTIONS.put("住房", new BigDecimal("1200"));
        SPECIAL_DEDUCTIONS.put("子女教育", new BigDecimal("1000"));
        SPECIAL_DEDUCTIONS.put("继续教育", new BigDecimal("400"));
        SPECIAL_DEDUCTIONS.put("大病医疗", new BigDecimal("8000")); // 年度上限
        SPECIAL_DEDUCTIONS.put("房贷利息", new BigDecimal("1000"));
        SPECIAL_DEDUCTIONS.put("住房租金", new BigDecimal("1500"));
        SPECIAL_DEDUCTIONS.put("赡养老人", new BigDecimal("2000"));
    }  
    
    /**
     * 计算年度个人所得税
     * @param annualIncome 年度总收入
     * @param specialDeductions 专项扣除金额
     * @param additionalDeductions 专项附加扣除
     * @return 计算结果
     */
    public static TaxResult calculateAnnualTax(  
        double annualIncome,  
        double specialDeductions,  
        double additionalDeductions) {  
        
        // 基本扣除费用（年度）
        final double BASIC_DEDUCTION = 60000;  
        
        // 转换为 BigDecimal 确保精度
        BigDecimal income = BigDecimal.valueOf(annualIncome);
        BigDecimal special = BigDecimal.valueOf(specialDeductions);
        BigDecimal additional = BigDecimal.valueOf(additionalDeductions);
        BigDecimal basic = BigDecimal.valueOf(BASIC_DEDUCTION);
        
        // 计算应纳税所得额
        BigDecimal taxableIncome = income
            .subtract(special)
            .subtract(additional)
            .subtract(basic)
            .max(BigDecimal.ZERO); // 不能为负数
        
        // 查找适用税率
        TaxBracket bracket = findTaxBracket(taxableIncome.doubleValue());
        
        // 计算应纳税额
        BigDecimal taxAmount = taxableIncome
            .multiply(BigDecimal.valueOf(bracket.getRate()))
            .subtract(BigDecimal.valueOf(bracket.getQuickDeduction()));
        
        // 确保税额不为负数
        taxAmount = taxAmount.max(BigDecimal.ZERO);
        
        // 计算税后收入
        BigDecimal afterTaxIncome = income.subtract(taxAmount);
        
        return new TaxResult(
            income.doubleValue(),
            taxableIncome.doubleValue(),
            taxAmount.doubleValue(),
            afterTaxIncome.doubleValue(),
            bracket
        );
    }  
    
    /**
     * 根据应纳税所得额查找适用税率
     */
    private static TaxBracket findTaxBracket(double taxableIncome) {
        for (TaxBracket bracket : TAX_BRACKETS) {
            if (taxableIncome >= bracket.getLowerBound() && 
                taxableIncome < bracket.getUpperBound()) {
                return bracket;
            }
        }
        return TAX_BRACKETS[TAX_BRACKETS.length - 1];
    }  
    
    /**
     * 获取专项扣除标准
     */
    public static Map<String, BigDecimal> getSpecialDeductionStandards() {
        return new HashMap<>(SPECIAL_DEDUCTIONS);
    }  
    
    /**
     * 税率档次类
     */
    public static class TaxBracket {
        private final double lowerBound;
        private final double upperBound;
        private final double rate;
        private final double quickDeduction;
        
        public TaxBracket(double lowerBound, double upperBound,  
                        double rate, double quickDeduction) {
            this.lowerBound = lowerBound;
            this.upperBound = upperBound;
            this.rate = rate;
            this.quickDeduction = quickDeduction;
        }  
        
        // Getter 方法
        public double getLowerBound() { return lowerBound; }
        public double getUpperBound() { return upperBound; }
        public double getRate() { return rate; }
        public double getQuickDeduction() { return quickDeduction; }
        
        @Override
        public String toString() {
            return String.format("税率：%.1f%%, 速算扣除数：%.0f", rate * 100, quickDeduction);
        }
    }  
    
    /**
     * 计算结果类
     */
    public static class TaxResult {
        private final double totalIncome;          // 总收入
        private final double taxableIncome;        // 应纳税所得额
        private final double taxAmount;            // 应纳税额
        private final double afterTaxIncome;       // 税后收入
        private final TaxBracket taxBracket;       // 适用税率档次
        
        public TaxResult(double totalIncome, double taxableIncome,  
                        double taxAmount, double afterTaxIncome,
                        TaxBracket taxBracket) {
            this.totalIncome = totalIncome;
            this.taxableIncome = taxableIncome;
            this.taxAmount = taxAmount;
            this.afterTaxIncome = afterTaxIncome;
            this.taxBracket = taxBracket;
        }  
        
        // Getter 方法
        public double getTotalIncome() { return totalIncome; }
        public double getTaxableIncome() { return taxableIncome; }
        public double getTaxAmount() { return taxAmount; }
        public double getAfterTaxIncome() { return afterTaxIncome; }
        public TaxBracket getTaxBracket() { return taxBracket; }
        
        @Override
        public String toString() {
            return String.format(
                "计算结果:\n" +
                "总收入：¥%.2f\n" +
                "应纳税所得额：¥%.2f\n" +
                "应纳税额：¥%.2f\n" +
                "税后收入：¥%.2f\n" +
                "适用税率：%s",
                totalIncome, taxableIncome, taxAmount, afterTaxIncome, taxBracket
            );
        }
    }
}

3. GUI 界面实现

package com.tax.calculator;

import javax.swing.*;
import javax.swing.border.TitledBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.math.BigDecimal;
import java.util.Map;

/**
 * 个税计算器主界面
 */
public class TaxCalculatorFrame extends JFrame {  
    
    private JTextField incomeField;
    private JTextField specialDeductionField;
    private JTextField additionalDeductionField;
    private JTextArea resultArea;
    private JComboBox<String> deductionTypeCombo;
    private JLabel standardLabel;  
    
    public TaxCalculatorFrame() {
        initUI();
        initData();
    }  
    
    private void initUI() {
        setTitle("个人所得税计算模拟器 v1.0");
        setSize(800, 600);
        setLocationRelativeTo(null);
        
        // 主面板
        JPanel mainPanel = new JPanel(new BorderLayout(10, 10));
        mainPanel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
        
        // 输入面板
        mainPanel.add(createInputPanel(), BorderLayout.NORTH);
        
        // 结果面板
        mainPanel.add(createResultPanel(), BorderLayout.CENTER);
        
        // 按钮面板
        mainPanel.add(createButtonPanel(), BorderLayout.SOUTH);
        
        add(mainPanel);
    }  
    
    private JPanel createInputPanel() {
        JPanel panel = new JPanel(new GridLayout(5, 2, 10, 10));
        panel.setBorder(BorderFactory.createTitledBorder(
            BorderFactory.createLineBorder(Color.GRAY),
            "个税计算参数输入",
            TitledBorder.LEFT,
            TitledBorder.TOP
        ));
        
        // 年度总收入
        panel.add(new JLabel("年度总收入 (¥):"));
        incomeField = new JTextField("120000");
        panel.add(incomeField);
        
        // 专项扣除
        panel.add(new JLabel("三险一金专项扣除 (¥):"));
        specialDeductionField = new JTextField("10000");
        panel.add(specialDeductionField);
        
        // 专项附加扣除
        panel.add(new JLabel("专项附加扣除 (¥):"));
        additionalDeductionField = new JTextField("3000");
        panel.add(additionalDeductionField);
        
        // 扣除标准查询
        panel.add(new JLabel("扣除项目查询:"));
        JPanel queryPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
        deductionTypeCombo = new JComboBox<>();
        queryPanel.add(deductionTypeCombo);
        standardLabel = new JLabel("标准：¥0");
        queryPanel.add(standardLabel);
        panel.add(queryPanel);
        
        return panel;
    }  
    
    private JScrollPane createResultPanel() {
        resultArea = new JTextArea();
        resultArea.setEditable(false);
        resultArea.setFont(new Font("宋体", Font.PLAIN, 14));
        resultArea.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
        
        JScrollPane scrollPane = new JScrollPane(resultArea);
        scrollPane.setBorder(BorderFactory.createTitledBorder("计算结果"));
        
        return scrollPane;
    }  
    
    private JPanel createButtonPanel() {
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.CENTER, 20, 10));
        
        // 计算按钮
        JButton calculateBtn = new JButton("计算个税");
        calculateBtn.setFont(new Font("微软雅黑", Font.BOLD, 14));
        calculateBtn.setBackground(new Color(70, 130, 180));
        calculateBtn.setForeground(Color.WHITE);
        calculateBtn.setPreferredSize(new Dimension(120, 40));
        
        calculateBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                calculateTax();
            }
        });
        
        // 清除按钮
        JButton clearBtn = new JButton("清除结果");
        clearBtn.setFont(new Font("微软雅黑", Font.PLAIN, 14));
        clearBtn.setPreferredSize(new Dimension(120, 40));
        clearBtn.addActionListener(e -> clearResults());
        
        // 税率表按钮
        JButton rateTableBtn = new JButton("查看税率表");
        rateTableBtn.setFont(new Font("微软雅黑", Font.PLAIN, 14));
        rateTableBtn.setPreferredSize(new Dimension(120, 40));
        rateTableBtn.addActionListener(e -> showTaxRateTable());
        
        panel.add(calculateBtn);
        panel.add(clearBtn);
        panel.add(rateTableBtn);
        
        return panel;
    }  
    
    private void initData() {
        // 初始化扣除类型下拉框
        Map<String, BigDecimal> standards = TaxCalculator.getSpecialDeductionStandards();
        for (String key : standards.keySet()) {
            deductionTypeCombo.addItem(key);
        }
        
        // 添加下拉框监听
        deductionTypeCombo.addActionListener(e -> {
            String selected = (String) deductionTypeCombo.getSelectedItem();
            if (selected != null) {
                BigDecimal standard = standards.get(selected);
                standardLabel.setText(String.format("标准：¥%.2f", standard));
            }
        });
        
        // 默认选择第一个
        if (deductionTypeCombo.getItemCount() > 0) {
            deductionTypeCombo.setSelectedIndex(0);
        }
    }  
    
    /**
     * 执行个税计算
     */
    private void calculateTax() {
        try {
            // 获取输入值
            double income = Double.parseDouble(incomeField.getText());
            double special = Double.parseDouble(specialDeductionField.getText());
            double additional = Double.parseDouble(additionalDeductionField.getText());
            
            // 验证输入
            if (income < 0 || special < 0 || additional < 0) {
                JOptionPane.showMessageDialog(this,
                    "输入值不能为负数！",
                    "输入错误",
                    JOptionPane.WARNING_MESSAGE);
                return;
            }
            
            // 执行计算
            TaxCalculator.TaxResult result = TaxCalculator.calculateAnnualTax(
                income, special, additional);
            
            // 显示结果
            displayResult(result);
            
        } catch (NumberFormatException ex) {
            JOptionPane.showMessageDialog(this,
                "请输入有效的数字！",
                "输入错误",
                JOptionPane.ERROR_MESSAGE);
        }
    }  
    
    /**
     * 显示计算结果
     */
    private void displayResult(TaxCalculator.TaxResult result) {
        StringBuilder sb = new StringBuilder();
        sb.append("=== 个人所得税计算结果 ===\n\n");
        sb.append(String.format("年度总收入：¥%,.2f\n", result.getTotalIncome()));
        sb.append(String.format("应纳税所得额：¥%,.2f\n", result.getTaxableIncome()));
        sb.append(String.format("适用税率档次：%s\n", result.getTaxBracket()));
        sb.append(String.format("应纳个人所得税：¥%,.2f\n", result.getTaxAmount()));
        sb.append(String.format("年度税后收入：¥%,.2f\n\n", result.getAfterTaxIncome()));
        
        // 计算月度数据
        double monthlyTax = result.getTaxAmount() / 12;
        double monthlyAfterTax = result.getAfterTaxIncome() / 12;
        
        sb.append("=== 月度数据估算 ===\n");
        sb.append(String.format("月度平均纳税：¥%,.2f\n", monthlyTax));
        sb.append(String.format("月度税后收入：¥%,.2f\n\n", monthlyAfterTax));
        
        // 添加税务建议
        sb.append("=== 税务优化建议 ===\n");
        if (result.getTaxableIncome() > 0) {
            sb.append("1. 充分利用专项附加扣除项目\n");
            sb.append("2. 合理规划年度收入时间分布\n");
            sb.append("3. 符合条件的捐赠可税前扣除\n");
        } else {
            sb.append("当前收入无需缴纳个人所得税\n");
        }
        
        resultArea.setText(sb.toString());
        resultArea.setCaretPosition(0);
    }  
    
    /**
     * 显示税率表
     */
    private void showTaxRateTable() {
        StringBuilder sb = new StringBuilder();
        sb.append("=== 个人所得税税率表（综合所得） ===\n\n");
        sb.append("级数 | 全年应纳税所得额 | 税率 | 速算扣除数\n");
        sb.append("----|-----------------|------|----------\n");
        
        TaxCalculator.TaxBracket[] brackets = new TaxCalculator.TaxBracket[]{
            new TaxCalculator.TaxBracket(0, 36000, 0.03, 0),
            new TaxCalculator.TaxBracket(36000, 144000, 0.10, 2520),
            new TaxCalculator.TaxBracket(144000, 300000, 0.20, 16920),
            new TaxCalculator.TaxBracket(300000, 420000, 0.25, 31920),
            new TaxCalculator.TaxBracket(420000, 660000, 0.30, 52920),
            new TaxCalculator.TaxBracket(660000, 960000, 0.35, 85920),
            new TaxCalculator.TaxBracket(960000, Double.MAX_VALUE, 0.45, 181920)
        };
        
        for (int i = 0; i < brackets.length; i++) {
            TaxCalculator.TaxBracket b = brackets[i];
            String range;
            if (b.getUpperBound() == Double.MAX_VALUE) {
                range = String.format("超过%,.0f 元", b.getLowerBound());
            } else {
                range = String.format("%,.0f - %,.0f 元", 
                    b.getLowerBound(), b.getUpperBound());
            }
            
            sb.append(String.format("%-4d| %-15s | %.1f%% | %, .0f 元\n", 
                i + 1, range, b.getRate() * 100, b.getQuickDeduction()));
        }
        
        sb.append("\n注：应纳税所得额 = 年度收入 - 6 万元 (基本扣除) - 专项扣除 - 专项附加扣除\n");
        
        resultArea.setText(sb.toString());
    }  
    
    /**
     * 清除结果
     */
    private void clearResults() {
        resultArea.setText("");
    }
}

三、使用说明

1. 运行环境要求

• Java 8 或更高版本
• 支持 Swing 的桌面环境

2. 编译运行

# 编译所有 Java 文件
javac -d . com/tax/calculator/*.java

# 运行程序
java com.tax.calculator.PersonalIncomeTaxApp

3. 程序功能演示

1. 输入计算参数：
   • 年度总收入
   • 三险一金专项扣除
   • 专项附加扣除
2. 查询扣除标准：
   • 通过下拉框选择不同扣除项目
   • 查看各项目扣除标准
3. 计算个税：
   • 点击'计算个税'按钮
   • 查看详细计算结果
4. 查看税率表：
   • 点击'查看税率表'按钮
   • 了解各级税率信息

四、核心算法说明

1. 计算公式

应纳税所得额 = 年度收入 - 60000(基本减除费用) - 专项扣除 - 专项附加扣除
应纳税额 = 应纳税所得额 × 适用税率 - 速算扣除数

2. 税率表算法

采用逐级累进计算方式，通过查找表确定适用税率。

五、项目扩展建议

1. 数据持久化：添加文件保存/加载功能
2. 历史记录：记录多次计算结果
3. 导出功能：支持 PDF/Excel 导出
4. 联网更新：自动更新税率政策
5. 图表展示：使用 JFreeChart 添加图表

六、注意事项

1. 本程序为模拟器，实际报税请以官方系统为准
2. 税率政策如有更新，需要相应修改代码
3. 计算结果仅供参考，不构成税务建议

七、开源协议

本项目采用 MIT 开源协议，允许自由使用、修改和分发。