JAVA 简单练习——简单计算器
按照蓝桥云课实验，Java实现简单的计算器，运算逻辑简单。
主要是为了熟悉Java 中的图形化编程，相较于MFC编程，简单清晰，注意对按键事件的注册和监听。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.math.BigDecimal;
import java.security.Key;
import java.util.Vector;
public class Calculator {
JFrame frame = new JFrame("Calculator");
String str1 = "";
String str2 = "";
String signal = "";
String result = "";
JButton store;
Vector vt = new Vector(20, 10);
//状态变量
int k1 = 1;// 开关1用于选择输入方向，将要写入str1或str2// 为 1 时写入 str1，为 2 时写入 str2
int k2 = 1;// 开关 2 用于记录符号键的次数//如果 k2>1 说明进行的是 2+3-9+8 这样的多符号运算
int k3 = 1;// 开关3用于标识 str1 是否可以被清 0// 等于 1 时可以，不等于1时不能被清0
int k4 = 1;// 开关4用于标识 str2 是否可以被清 0// 等于 1 时可以，不等于1时不能被清0
int k5 = 1;// 开关5用于控制小数点可否被录入// 等于1时可以，不为1时，输入的小数点被丢掉
//所需组件
JTextField result_TextField = new JTextField(result,20);
//清除按钮
JButton clear_Button = new JButton("clear");
//数字按钮
JButton button0 = new JButton("0");
JButton button1 = new JButton("1");
JButton button2 = new JButton("2");
JButton button3 = new JButton("3");
JButton button4 = new JButton("4");
JButton button5 = new JButton("5");
JButton button6 = new JButton("6");
JButton button7 = new JButton("7");
JButton button8 = new JButton("8");
JButton button9 = new JButton("9");
//操作符按钮
JButton button_Dian = new JButton(".");
JButton button_jia = new JButton("+");
JButton button_jian = new JButton("-");
JButton button_cheng = new JButton("*");
JButton button_chu = new JButton("/");
//等于号按钮
JButton button_dy = new JButton("=");
Calculator() {
button0.setMnemonic(KeyEvent.VK_0);//按下Alt+0
button1.setMnemonic(KeyEvent.VK_1);//按下Alt+1
button2.setMnemonic(KeyEvent.VK_2);//按下Alt+2
button3.setMnemonic(KeyEvent.VK_3);//按下Alt+3
button4.setMnemonic(KeyEvent.VK_4);//按下Alt+4
button5.setMnemonic(KeyEvent.VK_5);//按下Alt+5
button6.setMnemonic(KeyEvent.VK_6);//按下Alt+6
button7.setMnemonic(KeyEvent.VK_7);//按下Alt+7
button8.setMnemonic(KeyEvent.VK_8);//按下Alt+8
button9.setMnemonic(KeyEvent.VK_9);//按下Alt+9
button_jia.setMnemonic(KeyEvent.VK_PLUS);
button_jian.setMnemonic(KeyEvent.VK_SUBTRACT);
button_cheng.setMnemonic(KeyEvent.VK_MULTIPLY);
button_chu.setMnemonic(KeyEvent.VK_DIVIDE);
button_dy.setMnemonic(KeyEvent.VK_EQUALS);
button_Dian.setMnemonic(KeyEvent.VK_P);
clear_Button.setMnemonic(KeyEvent.VK_C);
//面板
JPanel pan = new JPanel();
pan.setLayout(new GridLayout(4, 4, 5, 5));
pan.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
pan.add(button7);
pan.add(button8);
pan.add(button7);
pan.add(button8);
pan.add(button9);
pan.add(button_chu);
pan.add(button4);
pan.add(button5);
pan.add(button6);
pan.add(button_cheng);
pan.add(button1);
pan.add(button2);
pan.add(button3);
pan.add(button_jian);
pan.add(button0);
pan.add(button_Dian);
pan.add(button_dy);
pan.add(button_jia);
JPanel pan2 = new JPanel();
pan2.setLayout(new BorderLayout());
pan2.add(result_TextField, BorderLayout.WEST);
pan2.add(clear_Button, BorderLayout.EAST);
frame.getContentPane().setLayout(new BorderLayout());
frame.getContentPane().add(pan2, BorderLayout.NORTH);
frame.getContentPane().add(pan, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
class Listener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
String ss = ((JButton) e.getSource()).getText();
store = (JButton) e.getSource();
vt.add(store);
if (k1 == 1) {
if (k3 == 1) {
str1 = "";
k5 = 1;
}
str1 = str1 + ss;
k3 += 1;//保证第一个数不被清空
result_TextField.setText(str1);
} else if (k1 == 2) {
if (k4 == 1) {
str2 = "";
k5 = 1;
}
str2 = str2 + ss;
k4 += 1;
result_TextField.setText(str2);
}
}
}
class Listener_xiaos implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
store = (JButton) e.getSource();
vt.add(store);
if (k5 == 1) {
String ss2 = ((JButton) e.getSource()).getText();
if (k1 == 1) {
if (k3 == 1) {
str1 = "";
k5 = 1;
}
str1 = str1 + ss2;
k3 += 1;//保证第一个数不被清空
result_TextField.setText(str1);
} else if (k1 == 2) {
if (k4 == 1) {
str2 = "";
k5 = 1;
}
str2 = str2 + ss2;
k4 += 1;
result_TextField.setText(str2);
}
}
k5 += 1;
}
}
class Listener_signal implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
String ss2 = ((JButton) e.getSource()).getText();
store = (JButton) e.getSource();
vt.add(store);
if (k2 == 1) {
k1 = 2;
k5 = 1;
signal = ss2;
k2 = k2 + 1;
} else {
int a = vt.size();
JButton c = (JButton) vt.get(a - 2);
if (!(c.getText().equals("+"))
&& !(c.getText().equals("-"))
&& !(c.getText().equals("*"))
&& !(c.getText().equals("/"))) {
cal();
str1 = result;
// 开关 k1 为 1 时，向数 1 写值，为2时向数2写
k1 = 2;
k5 = 1;
k4 = 1;
signal = ss2;
}
k2 = k2 + 1;
}
}
}
class Listener_dy implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
store = (JButton) e.getSource();
vt.add(store);
cal();
// 还原开关k1状态
k1 = 1;
// 还原开关k2状态
k2 = 1;
// 还原开关k3状态
k3 = 1;
// 还原开关k4状态
k4 = 1;
// 为 7+5=12 +5=17 这种计算做准备
str1 = result;
}
}
class Listener_clear implements ActionListener {
@SuppressWarnings("unchecked")
public void actionPerformed(ActionEvent e) {
store = (JButton) e.getSource();
vt.add(store);
k5 = 1;
k2 = 1;
k1 = 1;
k3 = 1;
k4 = 1;
str1 = "0";
str2 = "0";
signal = "";
result = "";
result_TextField.setText(result);
vt.clear();
}
}
//监听等于键
Listener_dy jt_dy=new Listener_dy();
button_dy.addActionListener(jt_dy);
// 监听数字键
Listener jt=new Listener();
button7.addActionListener(jt);
button8.addActionListener(jt);
button9.addActionListener(jt);
button4.addActionListener(jt);
button5.addActionListener(jt);
button6.addActionListener(jt);
button1.addActionListener(jt);
button2.addActionListener(jt);
button3.addActionListener(jt);
button0.addActionListener(jt);
// 监听符号键
Listener_signal jt_signal=new Listener_signal();
button_jia.addActionListener(jt_signal);
button_jian.addActionListener(jt_signal);
button_cheng.addActionListener(jt_signal);
button_chu.addActionListener(jt_signal);
// 监听清除键
Listener_clear jt_c=new Listener_clear();
clear_Button.addActionListener(jt_c);
// 监听小数点键
Listener_xiaos jt_xs=new Listener_xiaos();
button_Dian.addActionListener(jt_xs);
// 窗体关闭事件的响应程序
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);//退出程序
}
});
}
public void cal(){
double a2;
double b2;
String c = signal;
double result2 = 0;
if(c.equals("")){
result_TextField.setText("Please input operator");
}else{
if(str1.equals("."))
str1 = "0.0";
if(str2.equals("."))
str2 = "0.0";
a2 = Double.valueOf(str1).doubleValue();
b2 = Double.valueOf(str2).doubleValue();
if (c.equals("+")) {
result2 = a2 + b2;
}
if (c.equals("-")) {
result2 = a2 - b2;
}
if (c.equals("*")) {
BigDecimal m1 = new BigDecimal(Double.toString(a2));
BigDecimal m2 = new BigDecimal(Double.toString(b2));
result2 = m1.multiply(m2).doubleValue();
}
if (c.equals("/")) {
if (b2 == 0) {
result2 = 0;
} else {
result2 = a2 / b2;
}
}
result = String.valueOf(result2);
result_TextField.setText(result);
}
}
public static void main(String[] args) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch (Exception e) {
e.printStackTrace();
}
Calculator c = new Calculator();
}
}