java 计算器

Posted 2022-12-09 夏芷雨涵梦

题目：简易计算器

时间：2019.3.10

介绍：做一个简易的计算器，实现简单的加减乘除运算。本文代码在Eclipse上调试运行。

package calculate;

import javax.swing.*;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.*;

public class cal extends JFrame implements ActionListener 
	JMenuBar menubar = new JMenuBar();
	JMenu menu1, menu2, menu3;
	JMenuItem item1, item2, item3, item4, item5, item6, item7, item8;
	JTextField area = new JTextField("0");
	JPanel panel = new JPanel();
	String[] str =  "CE", "C", "%", "sqrt", "7", "8", "9", "/", "4", "5", "6",
			"*", "1", "2", "3", "-", "0", ".", "+", "=" ;
	JButton button[] = new JButton[str.length];
	double result = 0.0;
	boolean first = true;//是否是整个表达式的第一个数字,或者是运算符后的第一个数字 
	String operator = "=";//当前运算符
	cal() 
		init();
		setVisible(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	
	void init() 
		menu1 = new JMenu("查看");
		menu2 = new JMenu("编辑");
		menu3 = new JMenu("帮助");
		item1 = new JMenuItem("标准型");
		item2 = new JMenuItem("科学型");
		item3 = new JMenuItem("程序员");
		item4 = new JMenuItem("复制");
		item5 = new JMenuItem("粘贴");
		item6 = new JMenuItem("历史记录");
		item7 = new JMenuItem("帮助文件");
		item8 = new JMenuItem("关于计算器");
		menu1.add(item1);
		menu1.add(item2);
		menu1.add(item3);
		menu2.add(item4);
		menu2.add(item5);
		menu2.add(item6);
		menu3.add(item7);
		menu3.add(item8);
		menubar.add(menu1);
		menubar.add(menu2);
		menubar.add(menu3);
		setJMenuBar(menubar);
		area.setHorizontalAlignment(JTextField.RIGHT);
		area.setSize(200, 50);
		area.setBackground(Color.white);
		add(area, BorderLayout.NORTH);
		panel.setLayout(new GridLayout(5, 4, 3, 3));
		for (int i = 0; i < str.length; i++) 
			button[i] = new JButton(str[i]);
			panel.add(button[i]);
			button[i].setForeground(Color.blue);
			button[i].addActionListener(this);
		
		add(panel, BorderLayout.SOUTH);
	

	@Override
	public void actionPerformed(ActionEvent e) 
		// TODO 自动生成的方法存根
		String lable = e.getActionCommand();
		if ("0123456789.".indexOf(lable) >= 0) 
			handleNum(lable);
		 else if (lable.equals("CE")) 
			handleCe();
		 else if (lable.equals("C")) 
			handleC();
		 else 
			handle(lable);
		
	

	private void handle(String lable) 
		if (operator == "/") 
			if (getNumberFromText() == 0.0) 
				area.setText("除数不能为0");
			 else 
				result = result / getNumberFromText();
			
		 else if (operator == "*") 
			result = result * getNumberFromText();
		 else if (operator == "-") 
			result = result - getNumberFromText();
		 else if (operator == "+") 
			result = result + getNumberFromText();
		 else if (operator == "=") 
			result = getNumberFromText();
		 else if (operator == "%") 
			result = result / 100;
		 else if (operator == "sqrt") 
			result = Math.sqrt(result);
		
		area.setText(String.valueOf(result));
		// TODO 自动生成的方法存根
		first = true;
		operator = lable;
	

	private double getNumberFromText() 
		// TODO 自动生成的方法存根
		double num = 0.0;
		try 
			num = Double.valueOf(area.getText()).doubleValue();
		 catch (NumberFormatException e) 

		
		return num;
	

	private void handleC() 
		// TODO 自动生成的方法存根
		String text = area.getText();
		int i = text.length();
		if (i > 0) 
			text = text.substring(0, i - 1);
			if (text.length() == 0) 
				area.setText("0");
				first = true;
				operator = "=";
			 else 
				area.setText(text);
			
		
	

	private void handleNum(String key) 
		// TODO 自动生成的方法存根
		if (first) 
			area.setText(key);
		 else if ((key.equals(".")) && (area.getText().indexOf(".") < 0)) 
			area.setText(area.getText() + ".");
		 else if (!key.equals(".")) 
			area.setText(area.getText() + key);
		
		first = false;
	
	private void handleCe() 
		// TODO 自动生成的方法存根
		area.setText("0");
		first = true;
		operator = "=";
	

package calculate;
import javax.swing.JFrame;
public class main 
	public static void main(String[] args) 
		cal cal=new cal();
		cal.setTitle("计算器");
		cal.setVisible(true);
		cal.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		cal.setSize(400,300);
	

 运算截图：