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("u8BA1u7B97u5668")
		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：