简易计算器

package com.mine;import java.awt.BorderLayout;import java.awt.GridLayout;import java.awt.Panel;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JTextField;public class Calc extends JFrame {Panel pan1 = new Panel();Panel pan2 = new Panel();Panel pan3 = new Panel();JButton[] btn = new JButton[17];JTextField txt;static String sign;  //用来存储计算符static double temp ; //存储计算结果String[] str = { "7", "8", "9", "+", "4", "5", "6", "-", "1", "2", "3","*", "0", ".", "=", "/", "清空" }; //String数组用来存储按键信息public Calc(String name) {super(name);pan1.setLayout(new BorderLayout());pan2.setLayout(new GridLayout(4, 4));pan3.setLayout(new BorderLayout()); txt = new JTextField();this.setVisible(true);this.setSize(175, 220);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);this.setLocationRelativeTo(null);this.setResizable(false);for (int i = 0; i < btn.length; i++) {btn[i] = new JButton(str[i]);}for (int j = 0; j < btn.length; j++) {pan2.add(btn[j]);}for (int i = 0; i <btn.length; i++) {btn[i].addActionListener(new buttonlistener());//添加监听器}pan1.add(txt, "North");pan3.add(btn[16]);this.add(pan1, "North");this.add(pan2, "Center");this.add(pan3, "South");}class buttonlistener implements ActionListener{  //按钮监听事件,根据按键给不同德结果@Overridepublic void actionPerformed(ActionEvent e) {JButton btn = (JButton) e.getSource(); //获得数据源if (btn.getText().equals("=")) {Numeration();txt.setText(String.valueOf(temp));sign = "";} else if (btn.getText().equals("+")) {Numeration();txt.setText("");sign = "+";} else if (btn.getText().equals("-")) {Numeration();txt.setText("");sign = "-";} else if (btn.getText().equals("/")) {Numeration();txt.setText("");sign = "/";} else if (btn.getText().equals("*")) {Numeration();txt.setText("");sign = "*";} else {txt.setText(txt.getText() + btn.getText()); //文本框显示数字if (btn.getText() == "清空"){//点击清空按钮,则把所有信息重新赋为空txt.setText("");sign="";temp=0;}}}public void Numeration() {//编写具体计算方法if (sign == "+"){temp += Double.parseDouble(txt.getText());}else if (sign == "-"){temp -= Double.parseDouble(txt.getText());}else if (sign == "*"){temp *= Double.parseDouble(txt.getText());}else if (sign == "/"){temp /= Double.parseDouble(txt.getText());}else{//如果按=,则temp = Double.parseDouble(txt.getText());}}}public static void main(String[] args) {JFrame.setDefaultLookAndFeelDecorated(true);Calc c = new Calc("计算器");}}