利用 Java 开发一个可以进行简单的四则运算的图形化计算器，要求计算器至少能够实现基本的加减乘除运算以及实现括号功能。写出代码

好的，以下是一个简单的 Java 图形化计算器的代码，它可以实现基本的加减乘除运算以及实现括号功能：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField inputField;
    private JButton zeroBtn, oneBtn, twoBtn, threeBtn, fourBtn, fiveBtn, sixBtn, sevenBtn, eightBtn, nineBtn;
    private JButton addBtn, subtractBtn, multiplyBtn, divideBtn, equalsBtn, clearBtn, openParenBtn, closeParenBtn;
    private String currentInput = "";

    public Calculator() {
        setTitle("Calculator");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        inputField = new JTextField(20);
        inputField.setEditable(false);

        zeroBtn = new JButton("0");
        oneBtn = new JButton("1");
        twoBtn = new JButton("2");
        threeBtn = new JButton("3");
        fourBtn = new JButton("4");
        fiveBtn = new JButton("5");
        sixBtn = new JButton("6");
        sevenBtn = new JButton("7");
        eightBtn = new JButton("8");
        nineBtn = new JButton("9");
        addBtn = new JButton("+");
        subtractBtn = new JButton("-");
        multiplyBtn = new JButton("*");
        divideBtn = new JButton("/");
        equalsBtn = new JButton("=");
        clearBtn = new JButton("C");
        openParenBtn = new JButton("(");
        closeParenBtn = new JButton(")");

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4));
        buttonPanel.add(sevenBtn);
        buttonPanel.add(eightBtn);
        buttonPanel.add(nineBtn);
        buttonPanel.add(divideBtn);
        buttonPanel.add(fourBtn);
        buttonPanel.add(fiveBtn);
        buttonPanel.add(sixBtn);
        buttonPanel.add(multiplyBtn);
        buttonPanel.add(oneBtn);
        buttonPanel.add(twoBtn);
        buttonPanel.add(threeBtn);
        buttonPanel.add(subtractBtn);
        buttonPanel.add(zeroBtn);
        buttonPanel.add(openParenBtn);
        buttonPanel.add(closeParenBtn);
        buttonPanel.add(addBtn);

        JPanel clearPanel = new JPanel();
        clearPanel.add(clearBtn);

        Container contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());
        contentPane.add(inputField, BorderLayout.NORTH);
        contentPane.add(buttonPanel, BorderLayout.CENTER);
        contentPane.add(clearPanel, BorderLayout.SOUTH);

        zeroBtn.addActionListener(this);
        oneBtn.addActionListener(this);
        twoBtn.addActionListener(this);
        threeBtn.addActionListener(this);
        fourBtn.addActionListener(this);
        fiveBtn.addActionListener(this);
        sixBtn.addActionListener(this);
        sevenBtn.addActionListener(this);
        eightBtn.addActionListener(this);
        nineBtn.addActionListener(this);
        addBtn.addActionListener(this);
        subtractBtn.addActionListener(this);
        multiplyBtn.addActionListener(this);
        divideBtn.addActionListener(this);
        equalsBtn.addActionListener(this);
        clearBtn.addActionListener(this);
        openParenBtn.addActionListener(this);
        closeParenBtn.addActionListener(this);

        pack();
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == zeroBtn) {
            currentInput += "0";
        } else if (e.getSource() == oneBtn) {
            currentInput += "1";
        } else if (e.getSource() == twoBtn) {
            currentInput += "2";
        } else if (e.getSource() == threeBtn) {
            currentInput += "3";
        } else if (e.getSource() == fourBtn) {
            currentInput += "4";
        } else if (e.getSource() == fiveBtn) {
            currentInput += "5";
        } else if (e.getSource() == sixBtn) {
            currentInput += "6";
        } else if (e.getSource() == sevenBtn) {
            currentInput += "7";
        } else if (e.getSource() == eightBtn) {
            currentInput += "8";
        } else if (e.getSource() == nineBtn) {
            currentInput += "9";
        } else if (e.getSource() == addBtn) {
            currentInput += "+";
        } else if (e.getSource() == subtractBtn) {
            currentInput += "-";
        } else if (e.getSource() == multiplyBtn) {
            currentInput += "*";
        } else if (e.getSource() == divideBtn) {
            currentInput += "/";
        } else if (e.getSource() == openParenBtn) {
            currentInput += "(";
        } else if (e.getSource() == closeParenBtn) {
            currentInput += ")";
        } else if (e.getSource() == equalsBtn) {
            try {
                String result = evaluate(currentInput);
                inputField.setText(result);
                currentInput = "";
            } catch (Exception ex) {
                inputField.setText("Error");
                currentInput = "";
            }
        } else if (e.getSource() == clearBtn) {
            inputField.setText("");
            currentInput = "";
        }
        inputField.setText(currentInput);
    }

    public static String evaluate(String expression) {
        char[] tokens = expression.toCharArray();

        Stack<Integer> values = new Stack<Integer>();

        Stack<Character> ops = new Stack<Character>();

        for (int i = 0; i < tokens.length; i++) {
            if (tokens[i] == ' ')
                continue;

            if (tokens[i] >= '0' && tokens[i] <= '9') {
                StringBuffer sbuf = new StringBuffer();
                while (i < tokens.length && tokens[i] >= '0' && tokens[i] <= '9')
                    sbuf.append(tokens[i++]);
                values.push(Integer.parseInt(sbuf.toString()));
            }

            else if (tokens[i] == '(')
                ops.push(tokens[i]);

            else if (tokens[i] == ')') {
                while (ops.peek() != '(')
                    values.push(applyOp(ops.pop(), values.pop(), values.pop()));
                ops.pop();
            }

            else if (tokens[i] == '+' || tokens[i] == '-' || tokens[i] == '*' || tokens[i] == '/') {
                while (!ops.empty() && hasPrecedence(tokens[i], ops.peek()))
                    values.push(applyOp(ops.pop(), values.pop(), values.pop()));
                ops.push(tokens[i]);
            }
        }

        while (!ops.empty())
            values.push(applyOp(ops.pop(), values.pop(), values.pop()));

        return Integer.toString(values.pop());
    }

    public static boolean hasPrecedence(char op1, char op2) {
        if (op2 == '(' || op2 == ')')
            return false;
        if ((op1 == '*' || op1 == '/') && (op2 == '+' || op2 == '-'))
            return false;
        else
            return true;
    }

    public static int applyOp(char op, int b, int a) {
        switch (op) {
            case '+':
                return a + b;
            case '-':
                return a - b;
            case '*':
                return a * b;
            case '/':
                if (b == 0)
                    throw new UnsupportedOperationException("Cannot divide by zero");
                return a / b;
        }
        return 0;
    }

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

希望这个例子能够帮助你实现自己的图形化计算器。