5. Write a calculator program

5. Write a calculator program

"Red part for Answer"

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

 

Public class Calculator Extendsjframe implements ActionListener {

JTextField result; Displays the numbers and results of the input

int calculate_type = 0;//0, no operations; 1, 2, 3, 4 represent subtraction respectively

  

Calculator () {

JPanel JP;

JButton JB;

JP = new JPanel ();

jp.setlayout (New BorderLayout ());

     

//Create a text bar, do not allow editing, add to the top of the window

Result = new JTextField ();

result.seteditable (false);

Jp.add (Result,borderlayout.north);

     

///Window Center Add Number button, empty, backspace, decimal button

//Because borderlayout divides the windows into five areas in the top and bottom, each region can only add one component

//So add Keypanel to the middle area and add a number button to the Keypanel to implement the container nesting

JPanel Keypanel = new JPanel ();

keypanel.setlayout (New GridLayout (5,3));

for (int i=1;i<=9;i++) {

JB = new JButton ("" +i);

Jb.addactionlistener (this);

Keypanel.add (JB);

      }

JB = new JButton ("0");

Keypanel.add (JB);

Jb.addactionlistener (this);

JB = new JButton ("Empty");

Keypanel.add (JB);

Jb.addactionlistener (this);

JB = new JButton ("backspace");

Keypanel.add (JB);

Jb.addactionlistener (this);

     

JB = new JButton (".");

Jb.addactionlistener (this);

Keypanel.add (JB);

     

JB = new JButton ("=");

Jb.addactionlistener (this);

Keypanel.add (JB);

     

Jp.add (keypanel,borderlayout.center);

     

JPanel Operatorpanel = new JPanel ();

operatorpanel.setlayout (Newgridlayout (4,1));

JB = new JButton ("+");

Jb.addactionlistener (this);

Operatorpanel.add (JB);

     

JB = new JButton ("-");

Jb.addactionlistener (this);

Operatorpanel.add (JB);

     

JB = new JButton ("*");

Jb.addactionlistener (this);

Operatorpanel.add (JB);

     

JB = new JButton ("/");

Jb.addactionlistener (this);

Operatorpanel.add (JB);

Jp.add (operatorpanel,borderlayout.east);

     

//Add JPanel container to form

Setcontentpane (JP);

     

//Set the title, size, visibility, and close action of the form

settitle ("calculator");

setSize (340,260);

setvisible (true);

//Settings window closes, program exits

setdefaultcloseoperation (jframe.exit_on_close);

   }

  

Public void actionperformed (ActionEvent e) {

String cmd = E.getactioncommand ();

String C = result.gettext ();

     

if (cmd.equals ("Empty")) {

Result.settext ("");

      }

Else if (Cmd.compareto ("0") >=0 && Cmd.compareto ("9") <= 0) {

Result.settext (c + cmd);

      }

Else if (cmd.equals ("+") | | cmd.equals ("-") | | cmd.equals ("*") | | cmd.equals ("/")) {

if (Calculate_type = = 0) {//The first click operator since the last calculation is completed

Result.settext (c + cmd);

Judgecalculatetype (cmd);//Judge the type of calculation

        }

else{//Since the last time the calculation is complete, the second click Operator, triggering the calculation

calculate ();

Result.settext (Result.gettext () + cmd);

Judgecalculatetype (cmd);//Judge the type of calculation

        }

      }

Else if (cmd.equals ("=")) {//click = for calculation

try{

calculate ();

        }

catch (Exception exp) {

Joptionpane.showmessagedialog (This, "Input error, please check output or restart program");

        }

      }    

   }

  

//Judge the type of calculation

private void Judgecalculatetype (String cmd) {

if (cmd.equals ("+"))

calculate_type = 1;//record operation type

Else if (cmd.equals ("-"))

calculate_type = 2;

Else if (cmd.equals ("*"))

calculate_type = 3;

Else

calculate_type = 4;

   }

  

//Complete the calculation function

private void Calculate () {

double rt,op1,op2;

String C = result.gettext ();

int pos;

char ops[] = new char[]{' + ', '-', ' * ', '/'};

     

//Find operator Location

pos = C.indexof (ops[calculate_type-1]);

     

//The operator position is the dividing point, separating out two count to be counted

OP1 = double.parsedouble (c.substring (0, POS));

OP2 = double.parsedouble (c.substring (pos + 1));

     

switch (calculate_type) {

Case 1:

RT = Op1 + op2;

Break ;

Case 2:

RT = OP1-OP2;

Break ;

Case 3:

RT = OP1 * OP2;

Break ;

Case 4:

RT = OP1/OP2;

Break ;

Default:

rt = 0;

      }

     

Result.settext ("" + RT); Show calculation results

calculate_type = 0;//prepare to record the next calculation type

   }

  

Public static void Main (string[] args) {

new Calculator ();

   }

}