Simple Calculator using Java and NetBeans

Requirements:-

Java

Java Swing

NetBeans IDE

Function:-

It can do addition, substraction, multiplication, division and change the sign of number. We can also enter decimal number.

Code:-

package calculations;

/**
 *
 * @author HP
 */
public class calculators extends javax.swing.JFrame {
    double firstNumber;
    double secondNumber;
    double result;
    String operations;
    /**
     * Creates new form calculators
     */
    public calculators() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    //                           
    private void initComponents() {

        display = new javax.swing.JTextField();
        jbtn1 = new javax.swing.JButton();
        jbtn2 = new javax.swing.JButton();
        jbtn3 = new javax.swing.JButton();
        jbtn4 = new javax.swing.JButton();
        jbtn5 = new javax.swing.JButton();
        jbtn6 = new javax.swing.JButton();
        jbtn7 = new javax.swing.JButton();
        jbtn8 = new javax.swing.JButton();
        jbtn9 = new javax.swing.JButton();
        jbtn10 = new javax.swing.JButton();
        jbtn11 = new javax.swing.JButton();
        jbtn12 = new javax.swing.JButton();
        jbtn13 = new javax.swing.JButton();
        jbtn14 = new javax.swing.JButton();
        jbtn15 = new javax.swing.JButton();
        jbtn16 = new javax.swing.JButton();
        jbtn17 = new javax.swing.JButton();
        jbtn18 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        display.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        display.setHorizontalAlignment(javax.swing.JTextField.RIGHT);

        jbtn1.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn1.setText("1");
        jbtn1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn1ActionPerformed(evt);
            }
        });

        jbtn2.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn2.setText("2");
        jbtn2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn2ActionPerformed(evt);
            }
        });

        jbtn3.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn3.setText("3");
        jbtn3.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn3ActionPerformed(evt);
            }
        });

        jbtn4.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn4.setText("4");
        jbtn4.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn4ActionPerformed(evt);
            }
        });

        jbtn5.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn5.setText("5");
        jbtn5.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn5ActionPerformed(evt);
            }
        });

        jbtn6.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn6.setText("6");
        jbtn6.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn6ActionPerformed(evt);
            }
        });

        jbtn7.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn7.setText("7");
        jbtn7.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn7ActionPerformed(evt);
            }
        });

        jbtn8.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn8.setText("8");
        jbtn8.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn8ActionPerformed(evt);
            }
        });

        jbtn9.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn9.setText("9");
        jbtn9.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn9ActionPerformed(evt);
            }
        });

        jbtn10.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn10.setText("0");
        jbtn10.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn10ActionPerformed(evt);
            }
        });

        jbtn11.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn11.setText("+");
        jbtn11.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn11ActionPerformed(evt);
            }
        });

        jbtn12.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn12.setText("-");
        jbtn12.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn12ActionPerformed(evt);
            }
        });

        jbtn13.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn13.setText("*");
        jbtn13.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn13ActionPerformed(evt);
            }
        });

        jbtn14.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn14.setText("/");
        jbtn14.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn14ActionPerformed(evt);
            }
        });

        jbtn15.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn15.setText("+/-");
        jbtn15.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn15ActionPerformed(evt);
            }
        });

        jbtn16.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn16.setText(".");
        jbtn16.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn16ActionPerformed(evt);
            }
        });

        jbtn17.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn17.setText("C");
        jbtn17.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn17ActionPerformed(evt);
            }
        });

        jbtn18.setFont(new java.awt.Font("Segoe UI", 1, 18)); // NOI18N
        jbtn18.setText("=");
        jbtn18.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jbtn18ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(20, 20, 20)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                    .addComponent(display)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jbtn1, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn2, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn3, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn4, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jbtn5, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn6, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn7, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn8, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jbtn9, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn10, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn11, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jbtn12, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jbtn13, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jbtn14, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE))
                            .addComponent(jbtn17, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                        .addGap(18, 18, 18)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addComponent(jbtn18, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jbtn15, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jbtn16, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)))))
                .addContainerGap(20, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(17, 17, 17)
                .addComponent(display, javax.swing.GroupLayout.PREFERRED_SIZE, 47, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jbtn1, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn2, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn3, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn4, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jbtn5, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn6, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn7, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn8, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jbtn9, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn10, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn11, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn12, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jbtn13, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn14, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn15, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn16, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jbtn17, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jbtn18, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(21, Short.MAX_VALUE))
        );

        pack();
    }//                         

    private void jbtn18ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        String answer;
        secondNumber = Double.parseDouble(display.getText());
        if(operations == "+")
        {
            result = firstNumber + secondNumber ;
            answer = String.format("%.0f",result);
            display.setText(answer);
        }
        else if(operations == "-")
        {
            result = firstNumber - secondNumber ;
            answer = String.format("%.0f",result);
            display.setText(answer);
        }
        else if(operations == "*")
        {
            result = firstNumber * secondNumber ;
            answer = String.format("%.0f",result);
            display.setText(answer);
        }
        else if(operations == "/")
        {
            result = firstNumber / secondNumber ;
            answer = String.format("%.0f",result);
            display.setText(answer);
        }
    }                                      

    private void jbtn3ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn3.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn1ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn1.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn2ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn2.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn4ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn4.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn5ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn5.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn6ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn6.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn7ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn7.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn8ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn8.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn9ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn9.getText();
        display.setText(EnterNumber);
    }                                     

    private void jbtn10ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn10.getText();
        display.setText(EnterNumber);
        
    }                                      

    private void jbtn11ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        firstNumber = Double.parseDouble(display.getText());
        display.setText("");
        operations = "+";
    }                                      

    private void jbtn12ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        firstNumber = Double.parseDouble(display.getText());
        display.setText("");
        operations = "-";
    }                                      

    private void jbtn13ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        firstNumber = Double.parseDouble(display.getText());
        display.setText("");
        operations = "*";
    }                                      

    private void jbtn14ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        firstNumber = Double.parseDouble(display.getText());
        display.setText("");
        operations = "/";
    }                                      

    private void jbtn16ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        String EnterNumber = display.getText() + jbtn16.getText();
        display.setText(EnterNumber);
    }                                      

    private void jbtn15ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        double ops = Double.parseDouble(String.valueOf(display.getText()));
        ops = ops*(-1);
        display.setText(String.valueOf(ops));
    }                                      

    private void jbtn17ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        display.setText("");
    }                                      

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(calculators.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(calculators.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(calculators.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(calculators.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new calculators().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JTextField display;
    private javax.swing.JButton jbtn1;
    private javax.swing.JButton jbtn10;
    private javax.swing.JButton jbtn11;
    private javax.swing.JButton jbtn12;
    private javax.swing.JButton jbtn13;
    private javax.swing.JButton jbtn14;
    private javax.swing.JButton jbtn15;
    private javax.swing.JButton jbtn16;
    private javax.swing.JButton jbtn17;
    private javax.swing.JButton jbtn18;
    private javax.swing.JButton jbtn2;
    private javax.swing.JButton jbtn3;
    private javax.swing.JButton jbtn4;
    private javax.swing.JButton jbtn5;
    private javax.swing.JButton jbtn6;
    private javax.swing.JButton jbtn7;
    private javax.swing.JButton jbtn8;
    private javax.swing.JButton jbtn9;
    // End of variables declaration                   
}

Output:-