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简单计算器（Java实训）
实训目的：
掌握 Java GUI 开发中的布局管理和事件处理机制。
实训要求：
（1）要使用 java 的 GUI 设计出计算器界面。（2）通过界面 按钮，可以实现整数或浮点数的四则运算，并能将结果显示在界面中。（3） 计算可以有小数点，和正负整数的计算。（4）要有清零功能
新生第一次上路，借鉴了他人的代码，才造出这样一台计算器。 所以程序有少量BUG未解决： （1）精度不够，在计算1.3*6这样的数据会出现精度问题。 （2）未能控制小数点以及加减乘除不能连着输入问题。 （3）等于后算出结果，进行下一次不同数值计算时，不能将上一个结果自动清除。必须使用CE健手动清除。
本程序在计算结果，调用了JS功能，未写核心算法，主要还是学习设计GUI界面。
package program8;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.swing.JButton;
import javax.swing.JPanel;
import java.awt.GridLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.Font;
public class Test {
static String input = "";
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Test window = new Test();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Test() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setTitle("\u8BA1\u7B97\u5668");
frame.setBounds(100, 100, 400, 488);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextField textArea = new JTextField();
textArea.setFont(new Font("Monospaced", Font.PLAIN, 30));
textArea.setBounds(0, 0, 286, 96);
JButton btnCe = new JButton("CE");
btnCe.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnCe.getText();
set_text(textArea,text);
}
});
btnCe.setBounds(287, 0, 95, 94);
frame.getContentPane().setLayout(null);
frame.getContentPane().add(textArea);
frame.getContentPane().add(btnCe);
JPanel panel = new JPanel();
panel.setBounds(0, 96, 382, 344);
frame.getContentPane().add(panel);
panel.setLayout(new GridLayout(4, 4));
JButton btnNewButton = new JButton("7");
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton);
JButton btnNewButton_1 = new JButton("8");
btnNewButton_1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_1.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_1);
JButton btnNewButton_3 = new JButton("9");
btnNewButton_3.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_3.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_3);
JButton btnNewButton_4 = new JButton("/");
btnNewButton_4.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_4.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_4);
JButton btnNewButton_2 = new JButton("4");
btnNewButton_2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_2.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_2);
JButton btnNewButton_6 = new JButton("5");
btnNewButton_6.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_6.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_6);
JButton btnNewButton_5 = new JButton("6");
btnNewButton_5.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_5.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_5);
JButton btnNewButton_8 = new JButton("*");
btnNewButton_8.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_8.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_8);
JButton btnNewButton_12 = new JButton("1");
btnNewButton_12.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_12.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_12);
JButton btnNewButton_9 = new JButton("2");
btnNewButton_9.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_9.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_9);
JButton btnNewButton_7 = new JButton("3");
btnNewButton_7.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_7.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_7);
JButton btnNewButton_13 = new JButton("-");
btnNewButton_13.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_13.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_13);
JButton btnNewButton_10 = new JButton(".");
btnNewButton_10.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_10.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_10);
JButton btnNewButton_11 = new JButton("0");
btnNewButton_11.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_11.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_11);
JButton btnNewButton_14 = new JButton("=");
btnNewButton_14.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_14.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_14);
JButton btnNewButton_15 = new JButton("+");
btnNewButton_15.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text=btnNewButton_15.getText();
set_text(textArea,text);
}
});
panel.add(btnNewButton_15);
}
public static void set_text(JTextField tf,String s){
if(s.equals("=")){
//进行字符串表达式的运算
ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");
try{
input = String.valueOf(scriptEngine.eval(input));
tf.setText(input);
}catch(ScriptException e){
e.printStackTrace();
}
}
else if(s.equals("CE")){
input = "";
tf.setText(input);
}
else{
input = input + s;
tf.setText(input);
}
}
}
结果演示：   
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