java计算器2、8、10进制。切换进制时数据清空。

以下是一个简单的 Java 计算器，支持 2、8、10 进制的运算，并且在切换进制时会清空已经输入的数据：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField inputField;
    private JLabel modeLabel;
    private JButton[] numberButtons;
    private JButton[] operatorButtons;
    private JButton[] modeButtons;
    private int mode = 10;
    private String input = "";
    private boolean clearInput = false;

    public Calculator() {
        setTitle("Calculator");
        setSize(300, 250);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.setLayout(null);
        getContentPane().add(panel);

        inputField = new JTextField();
        inputField.setBounds(10, 10, 270, 30);
        inputField.setEditable(false);
        panel.add(inputField);

        modeLabel = new JLabel("Mode: 10");
        modeLabel.setBounds(10, 50, 60, 20);
        panel.add(modeLabel);

        numberButtons = new JButton[16];
        for (int i = 0; i < 10; i++) {
            numberButtons[i] = new JButton(String.valueOf(i));
            numberButtons[i].setBounds(i * 30 + 10, 80, 30, 30);
            numberButtons[i].addActionListener(this);
            panel.add(numberButtons[i]);
        }
        numberButtons[10] = new JButton("A");
        numberButtons[10].setBounds(10, 140, 30, 30);
        numberButtons[10].addActionListener(this);
        panel.add(numberButtons[10]);
        numberButtons[11] = new JButton("B");
        numberButtons[11].setBounds(40, 140, 30, 30);
        numberButtons[11].addActionListener(this);
        panel.add(numberButtons[11]);
        numberButtons[12] = new JButton("C");
        numberButtons[12].setBounds(70, 140, 30, 30);
        numberButtons[12].addActionListener(this);
        panel.add(numberButtons[12]);
        numberButtons[13] = new JButton("D");
        numberButtons[13].setBounds(100, 140, 30, 30);
        numberButtons[13].addActionListener(this);
        panel.add(numberButtons[13]);
        numberButtons[14] = new JButton("E");
        numberButtons[14].setBounds(130, 140, 30, 30);
        numberButtons[14].addActionListener(this);
        panel.add(numberButtons[14]);
        numberButtons[15] = new JButton("F");
        numberButtons[15].setBounds(160, 140, 30, 30);
        numberButtons[15].addActionListener(this);
        panel.add(numberButtons[15]);

        operatorButtons = new JButton[6];
        operatorButtons[0] = new JButton("+");
        operatorButtons[0].setBounds(200, 80, 30, 30);
        operatorButtons[0].addActionListener(this);
        panel.add(operatorButtons[0]);
        operatorButtons[1] = new JButton("-");
        operatorButtons[1].setBounds(200, 110, 30, 30);
        operatorButtons[1].addActionListener(this);
        panel.add(operatorButtons[1]);
        operatorButtons[2] = new JButton("*");
        operatorButtons[2].setBounds(200, 140, 30, 30);
        operatorButtons[2].addActionListener(this);
        panel.add(operatorButtons[2]);
        operatorButtons[3] = new JButton("/");
        operatorButtons[3].setBounds(230, 80, 30, 30);
        operatorButtons[3].addActionListener(this);
        panel.add(operatorButtons[3]);
        operatorButtons[4] = new JButton("=");
        operatorButtons[4].setBounds(230, 110, 30, 60);
        operatorButtons[4].addActionListener(this);
        panel.add(operatorButtons[4]);
        operatorButtons[5] = new JButton("C");
        operatorButtons[5].setBounds(10, 180, 60, 30);
        operatorButtons[5].addActionListener(this);
        panel.add(operatorButtons[5]);

        modeButtons = new JButton[3];
        modeButtons[0] = new JButton("2");
        modeButtons[0].setBounds(80, 50, 40, 20);
        modeButtons[0].addActionListener(this);
        panel.add(modeButtons[0]);
        modeButtons[1] = new JButton("8");
        modeButtons[1].setBounds(130, 50, 40, 20);
        modeButtons[1].addActionListener(this);
        panel.add(modeButtons[1]);
        modeButtons[2] = new JButton("10");
        modeButtons[2].setBounds(180, 50, 50, 20);
        modeButtons[2].addActionListener(this);
        panel.add(modeButtons[2]);

        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        if (command.equals("+")) {
            input += "+";
        } else if (command.equals("-")) {
            input += "-";
        } else if (command.equals("*")) {
            input += "*";
        } else if (command.equals("/")) {
            input += "/";
        } else if (command.equals("=")) {
            input = evaluate(input);
        } else if (command.equals("C")) {
            input = "";
            clearInput = true;
        } else if (command.equals("2")) {
            mode = 2;
            input = "";
            clearInput = true;
            modeLabel.setText("Mode: 2");
        } else if (command.equals("8")) {
            mode = 8;
            input = "";
            clearInput = true;
            modeLabel.setText("Mode: 8");
        } else if (command.equals("10")) {
            mode = 10;
            input = "";
            clearInput = true;
            modeLabel.setText("Mode: 10");
        } else {
            int value = Integer.parseInt(command, mode);
            input += Integer.toString(value, 10);
        }
        inputField.setText(input);
    }

    private String evaluate(String input) {
        String[] tokens = input.split(" ");
        int op1 = Integer.parseInt(tokens[0], mode);
        int op2 = Integer.parseInt(tokens[2], mode);
        int result = 0;
        switch (tokens[1]) {
            case "+":
                result = op1 + op2;
                break;
            case "-":
                result = op1 - op2;
                break;
            case "*":
                result = op1 * op2;
                break;
            case "/":
                result = op1 / op2;
                break;
        }
        return Integer.toString(result, mode);
    }

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

在上面的代码中，我们使用了一个 JTextField 来显示输入和输出的结果，用若干个 JButton 实现了数字、操作符和模式选择的按钮，并且通过实现 ActionListener 接口来处理按钮的事件。在 actionPerformed() 方法中，我们根据用户的选择更新 input 字符串的值，并且在 inputField 中显示出来。当用户选择模式切换时，我们需要重新设置 mode 变量的值，并且清空 input 字符串。当用户选择计算时，我们调用 evaluate() 方法来计算表达式的值，并且将结果以当前模式的形式显示在 inputField 中。

需要注意的是，当用户在切换模式时，我们需要将 clearInput 变量设置为 true，否则用户在输入数字时会出现错误。