java计算器依据输入信息计算结果并从文本框输出

你可以使用 Java 的 Swing 库来创建一个简单的计算器界面，然后使用 Java 的计算功能来计算输入的表达式。以下是一个简单的示例代码：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField inputField;
    private JButton[] numberButtons;
    private JButton[] operatorButtons;
    private JButton equalsButton;
    private JButton clearButton;
    
    public Calculator() {
        super("Calculator");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());
        
        inputField = new JTextField();
        add(inputField, BorderLayout.NORTH);
        
        JPanel buttonPanel = new JPanel(new GridLayout(4, 4));
        numberButtons = new JButton[10];
        for (int i = 0; i < 10; i++) {
            numberButtons[i] = new JButton("" + i);
            numberButtons[i].addActionListener(this);
            buttonPanel.add(numberButtons[i]);
        }
        
        operatorButtons = new JButton[4];
        operatorButtons[0] = new JButton("+");
        operatorButtons[1] = new JButton("-");
        operatorButtons[2] = new JButton("*");
        operatorButtons[3] = new JButton("/");
        for (int i = 0; i < 4; i++) {
            operatorButtons[i].addActionListener(this);
            buttonPanel.add(operatorButtons[i]);
        }
        
        equalsButton = new JButton("=");
        equalsButton.addActionListener(this);
        buttonPanel.add(equalsButton);
        
        clearButton = new JButton("C");
        clearButton.addActionListener(this);
        buttonPanel.add(clearButton);
        
        add(buttonPanel, BorderLayout.CENTER);
        
        pack();
        setVisible(true);
    }
    
    public void actionPerformed(ActionEvent e) {
        Object source = e.getSource();
        if (source == equalsButton) {
            String expression = inputField.getText();
            try {
                double result = evaluate(expression);
                inputField.setText("" + result);
            } catch (Exception ex) {
                inputField.setText("Error");
            }
        } else if (source == clearButton) {
            inputField.setText("");
        } else {
            String text = ((JButton)source).getText();
            inputField.setText(inputField.getText() + text);
        }
    }
    
    private double evaluate(String expression) throws Exception {
        String[] tokens = expression.split(" ");
        Stack<Double> stack = new Stack<Double>();
        for (String token : tokens) {
            if (isNumber(token)) {
                stack.push(Double.parseDouble(token));
            } else if (isOperator(token)) {
                double operand2 = stack.pop();
                double operand1 = stack.pop();
                double result = applyOperator(token, operand1, operand2);
                stack.push(result);
            } else {
                throw new Exception("Invalid expression");
            }
        }
        return stack.pop();
    }
    
    private boolean isNumber(String token) {
        try {
            Double.parseDouble(token);
            return true;
        } catch (NumberFormatException e) {
            return false;
        }
    }
    
    private boolean isOperator(String token) {
        return token.equals("+") || token.equals("-") || token.equals("*") || token.equals("/");
    }
    
    private double applyOperator(String operator, double operand1, double operand2) throws Exception {
        if (operator.equals("+")) {
            return operand1 + operand2;
        } else if (operator.equals("-")) {
            return operand1 - operand2;
        } else if (operator.equals("*")) {
            return operand1 * operand2;
        } else if (operator.equals("/")) {
            if (operand2 == 0) {
                throw new Exception("Division by zero");
            }
            return operand1 / operand2;
        } else {
            throw new Exception("Invalid operator");
        }
    }
    
    public static void main(String[] args) {
        new Calculator();
    }
}

这个计算器可以处理简单的四则运算，例如 "2 + 3 * 4"，并且可以处理错误情况，例如除以零。你可以在文本框中输入表达式，然后按下 "=" 按钮来计算结果。