java简易计算机（用栈实现中缀转后缀，计算后缀表达式）
Posted Icy Hunter
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这学期java课的一个小作业，用java编一个小计算器。
个人认为要点在于：
1.计算机的布局，即按钮和输出框的布局需要知道怎么操作，按钮的大小和字体的大小颜色、不同布局中按钮的改变大小等等
2.用栈将中缀表达式转换为后缀表达式
3.用栈将后缀表达式计算出来
其他问题应该不大，因为只是涉及到简单的加减乘除运算。
我的这个计算器有以下功能：
1.支持加减乘除运算，支持括号功能，小数点功能。
2.支持删除一位的操作。
3.支持计算结果继续进行计算的功能。
4.点击=后原表达式消失，只出现结果，一般保留一位小数。
目前发现的缺陷：
1.负数开头无法实现
2.输入错误表达式后，必须要再输入一次正确表达式后，才能正常开始运算，找不着bug，挺奇怪的，希望老师看不到
等等
但是我都通过trycatch将异常捕获，统一在界面输出操作“非法输入，请按两次AC后重新操作”。
以下是界面展示：
下面直接上代码了
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.*;
public class Computerhomework extends JFrame implements ActionListener
JTextField textField = new JTextField("");
String input = "";
JButton b[] = new JButton[20];
JPanel panel = new JPanel();
JPanel panel1 = new JPanel();
String name [] = "9","8","7","D","AC","6","5","4","-","(","3","2","1","*",")","0",".","=","/","+";
Stack<String> houzhui = new Stack<>();
public Computerhomework()
this.setTitle("Computer");
this.setSize(600, 700);
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
public void board()
textField.setPreferredSize(new Dimension(600,80));
textField.setFont(new Font("宋体",Font.PLAIN,30));
textField.setEditable(false);
panel1.add(textField);
panel.setLayout(new GridLayout(4,4,5,5));
panel1.setLayout(new FlowLayout(3));
this.add(panel, BorderLayout.CENTER);
this.add(panel1, BorderLayout.NORTH);
for(int i=0;i<name.length;i++)//添加按钮
b[i] = new JButton(name[i]);
b[i].setBackground(new Color(162,192,142));
b[i].setForeground(Color.BLACK); //设置按键颜色
b[i].setFont(new Font("宋体",Font.PLAIN,50));//设置字体格式
panel.add(b[i]);//将按键添加到界面
b[i].addActionListener(this);
@Override
public void actionPerformed(ActionEvent e)
int flag_feifa = 0;
try
for(int i = 0; i<name.length; i++)
if(e.getSource() == b[i] && name[i] == "AC")
textField.setText("");
input = "";
else if(e.getSource() == b[i] && name[i] == "D")
String t = textField.getText();
String flag = t.substring(t.length()-1);
if(flag.equals("+") || flag.equals("-") || flag.equals("*") || flag.equals("/") || flag.equals("(") || flag.equals(")"))
textField.setText(t.substring(0, t.length()-1));
input = input.substring(0,input.length() - 3);
else
textField.setText(t.substring(0, t.length()-1));
input = input.substring(0,input.length() - 1);
else if(e.getSource() == b[i] && name[i] =="(")
textField.setText(textField.getText() + e.getActionCommand() );
input +=e.getActionCommand() + " ";
else if(e.getSource() == b[i] && name[i] == ")")
textField.setText(textField.getText() + e.getActionCommand() );
input += " "+e.getActionCommand();
else if(e.getSource() == b[i] && name[i] == "=")
System.out.println(input);
String r = result(to_houzhui(input));
input = r;
textField.setText(r);
else if(e.getSource() == b[i] && (name[i] == "+" || name[i] == "-" || name[i]=="*" || name[i] =="/"))
textField.setText(textField.getText() + e.getActionCommand() );
input += " " + e.getActionCommand() + " ";
else if(e.getSource() == b[i])
textField.setText(textField.getText() + e.getActionCommand() );
input += e.getActionCommand();
catch(Exception x)
textField.setText("非法输入，请按两次AC后重新操作");
input = "";
flag_feifa = 1;
public String to_houzhui(String in)
String hou = "";
String s[] = in.split(" ");
// System.out.println(s.length);
// for(String t:s)
// System.out.println(t);
//
for(int i=0; i<s.length; i++)
// .getClass().toString()获取数据类型 1*1*1*(11+1-44*21/11)
char flag = s[i].charAt(0); //取出字符串的第一个字符作为判断
if(flag >= '0' && flag <= '9' && i==0)
hou += s[i]; //数字加入后缀表达式
else if(flag >= '0' && flag <= '9')
hou += " "+s[i]; //数字加入后缀表达式
else if(houzhui.empty() == true)
houzhui.push(s[i]); //栈为空直接入栈
else if(flag == '(') houzhui.push(s[i]);
else if(houzhui.peek().equals("("))
houzhui.push(s[i]); //栈顶为左括号,入栈
else if(flag == ')')
while(houzhui.peek().equals("(") != true)
hou += " "+houzhui.peek();
houzhui.pop();
houzhui.pop(); //将(也pop掉
else if((flag == '+' || flag == '-') && (houzhui.peek().equals("*") || houzhui.peek().equals("/") || houzhui.peek().equals("+") || houzhui.peek().equals("-")))
//低优先级遇到高优先级,高优先级出栈,低优先级入栈,平级也是先出再入
String f = houzhui.peek();
while((f.equals("+") || f.equals("-")||f.equals("*")||f.equals("/"))&&!houzhui.empty())
hou += " " + f;
houzhui.pop();
if(!houzhui.empty())f = houzhui.peek();
houzhui.push(s[i]);
else if((flag == '*' || flag == '/' )&& (houzhui.peek().equals("+")|| houzhui.peek().equals("-")))
//*/为这里最高阶的运算符,遇到低级压入栈12*(12+12-14*13)
houzhui.push(s[i]);
else
//最高级遇到同级,先出后进
String f = houzhui.peek();
while((f.equals("*") || f.equals("/"))&&!houzhui.empty() )
hou += " " + f;
houzhui.pop();
if(!houzhui.empty())f = houzhui.peek();
houzhui.push(s[i]);
while(!houzhui.empty())
hou += " "+houzhui.peek();
houzhui.pop();
return hou;
public String result(String s)
double sum = 0;
String item[] = s.split(" ");
Stack<String> res = new Stack<>();
for(int i=0; i<item.length; i++)
if(item[i].charAt(0)>'0' && item[i].charAt(0)<'9')
res.push(item[i]);
else if(item[i].equals("+"))
double x = Double.parseDouble(res.peek());
res.pop();
double y = Double.parseDouble(res.peek());
res.pop();
String z = String.valueOf(y+x);
res.push(z);
else if(item[i].equals("-"))
double x = Double.parseDouble(res.peek());
res.pop();
double y = Double.parseDouble(res.peek());
res.pop();
String z = String.valueOf(y-x);
res.push(z);
else if(item[i].equals("*"))
double x = Double.parseDouble(res.peek());
res.pop();
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