java编写的计算器

import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Calculator extends JFrame implements ActionListener private JTextField text; / 显示计算结果的文本行private char op; / 当前运算符private double value; / 当前计算结果值private boolean first; / 表示是否为数值的第 1 个数字private boolean cal; / 是否为连续运算boolean clickable; / 控制运算符是否可用boolean isTrue; / 控制数字键是否可用int sign; / 标志是什么原因导致异常public Calculator() / TODO Auto-generated const ructor stubsuper(“计算器“);this.setSize(280, 210);this.setLocation(300, 240);this.setDefaultCloseOperation(EXIT_ON_CLOSE);text = new JTextField(“0.“, 30);text.setHorizontalAlignment(JTextField.RIGHT); / 设置对齐方式，右对齐text.setEditable(false); / 只能显示，不允许编辑this.getContentPane().add(text, “North“);JPanel panel = new JPanel(new GridLayout(5, 4, 5, 5);/ 面板采用网格布局this.getContentPane().add(panel);String str = “sqrt“, “+/-“, “Backspace“, “C“, “7“, “8“, “9“, “/“,“4“, “5“, “6“, “*“, “1“, “2“, “3“, “-“, “0“, “.“, “=“, “+“ ;JButton buttons = new JButtonstr.length;for (int i = 0; i = 0 first = false;text.setText(text.getText() + current);clickable = true;if (current = “+“ | current = “-“ | current = “*“ | current = “/“)op = current.charAt(0);cal = true; else / 连续运算display();op = current.charAt(0); / 取第二个运算符text.setText(“ + value);first = true;clickable = false;isTrue = true;if (current = “=“ text.setText(“ + value);cal = false;first = true;clickable = false;isTrue = true;if (current = “.“ clickable = false;if (current = “sqrt“ if (value 0) this.sign = 2;clickable = false;isTrue = false;throw new ArithmeticException(); elsevalue = Math.sqrt(value); else display();cal = false;if (value 0) this.sign = 2;clickable = false;isTrue = false;throw new ArithmeticException(); elsevalue = Math.sqrt(value);first = false;isTrue = false;text.setText(“ + value);if (current = “+/-“ else display();cal = false;value = -value;first = false;isTrue = false;text.setText(“ + value); catch (ArithmeticException ae) if (sign = 1)text.setText(“除数不能为零!“);if (sign = 2)text.setText(“负数没有