import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

/**
*/
public class Calculator extends JFrame{

private JTextField textField;

private String operand1 = "";
private String operator = "";
private String operand2 = "";

private boolean forOperand1 = true;

public Calculator(){
   init();
}

private void init(){
   JMenuBar menuBar = new JMenuBar();

   JMenu fileMenu = new JMenu("File");
   JMenu helpMenu = new JMenu("Help");
   JMenuItem closeMenu = new JMenuItem("Close");

   closeMenu.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
            closeFrame();
         }
   });

   fileMenu.add(closeMenu);
   menuBar.add(fileMenu);
   menuBar.add(helpMenu);

   GridBagLayout gridLayout = new GridBagLayout();

   JPanel panel = new JPanel();
   panel.setLayout(gridLayout);

   GridBagConstraints c = new GridBagConstraints();
   c.fill = GridBagConstraints.HORIZONTAL;

   textField = new JTextField();
   textField.setEditable(false);
   c.weightx = 1;
   c.gridx = 0;
   c.gridy = 0;
   c.gridwidth = 5;
   panel.add(textField, c);

   c.fill = GridBagConstraints.HORIZONTAL;

   CButton backButton = new CButton("Backspace");
   c.weightx = 0.5;
   c.gridx = 0;
   c.gridy = 1;
   c.gridwidth = 2;
   panel.add(backButton, c);

   c.gridwidth = 1;
   c.weightx = 1;
//
   CButton ceButton = new CButton("CE");
   // c.weightx = 0.2;
   c.gridx = 3;
   c.gridy = 1;
   panel.add(ceButton, c);

   CButton cButton = new CButton("C");
   // c.weightx = 0.2;
   c.gridx = 4;
   c.gridy = 1;
   panel.add(cButton, c);

   // GridLayout gridLayout1 = new GridLayout(4, 5, 0, 0);
   //JPanel keyPanel = new JPanel();
   //keyPanel.setLayout(gridLayout1);

   c.gridwidth = 1;
   int operands = 0;
   for(int i=0; i < 4; i++){

         for(int j=0; j<5; j++){
            c.gridx = j;
            c.gridy = 3+i;

            operands = 7-(3*i) +j;

            if(i < 3 && j < 3){
               panel.add(new CButton(operands), c);
            }else if(i == 0){
               if(j == 3){
                     panel.add(new CButton("/"), c);
               }else{
                     panel.add(new CButton("sqrt"), c);
               }
            }else if(i == 1){
               if(j == 3){
                     panel.add(new CButton("*"), c);
               }else{
                     panel.add(new CButton("1/x"), c);
               }
            }else if(i == 2){
               if(j == 3){
                     panel.add(new CButton("-"), c);
               }else{
                     panel.add(new CButton("%"), c);
               }
            }
            else if(i ==3){
               if(j==0){
                     panel.add(new CButton(0), c);
               }else if(j==1){
                     panel.add(new CButton("+/-"), c);
               }else if(j==2){
                     panel.add(new CButton("."), c);
               }else if(j==3){
                     panel.add(new CButton("+"), c);
               }else if(j==4){
                     panel.add(new CButton("="), c);
               }
            }
         }
   }

   setTitle("Calculator");
   setJMenuBar(menuBar);
   setSize(280, 220);

   add(panel);
   setVisible(true);
   //pack();
   setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

}

private void closeFrame(){
   System.exit(0);
}

public static void main(String[] args){
   Calculator calculator = new Calculator();
}

private class CButton extends JButton implements ActionListener{

   boolean isOperator = false;

   int value = 0;

Sudoku Solution Verifier â Given a 9-by-9 array of integers betw...

Sudoku Solution Verifier â Given a 9-by-9 array of integers betw...