Phương trình bậc 2

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package ptbac2;

import javax.swing.JOptionPane;

/**
 *
 * @author leo
 */
public class Bac2 extends javax.swing.JFrame {

    /**
     * Creates new form Bac2
     */
    public Bac2() {
        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")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        tfA = new javax.swing.JTextField();
        tfB = new javax.swing.JTextField();
        tfC = new javax.swing.JTextField();
        lbResult = new javax.swing.JLabel();
        btCalc = new javax.swing.JButton();
        btClear = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 12)); // NOI18N
        jLabel1.setText("ax^2 + bx + c = 0");

        jLabel2.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        jLabel2.setText("a=");

        jLabel3.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        jLabel3.setText("b=");

        jLabel4.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        jLabel4.setText("c=");

        lbResult.setFont(new java.awt.Font("Times New Roman", 1, 14)); // NOI18N
        lbResult.setText("Result");

        btCalc.setText("Calc");
        btCalc.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btCalcActionPerformed(evt);
            }
        });

        btClear.setText("Clear");
        btClear.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btClearActionPerformed(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(47, 47, 47)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel2)
                    .addComponent(jLabel3)
                    .addComponent(jLabel4))
                .addGap(34, 34, 34)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(lbResult)
                    .addComponent(jLabel1)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                        .addGroup(layout.createSequentialGroup()
                            .addComponent(btCalc)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 42, Short.MAX_VALUE)
                            .addComponent(btClear))
                        .addComponent(tfA, javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(tfB, javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(tfC, javax.swing.GroupLayout.Alignment.LEADING)))
                .addContainerGap(65, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(27, 27, 27)
                .addComponent(jLabel1)
                .addGap(26, 26, 26)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(tfA, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(22, 22, 22)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(tfB, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(21, 21, 21)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel4)
                    .addComponent(tfC, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(34, 34, 34)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btCalc)
                    .addComponent(btClear))
                .addGap(36, 36, 36)
                .addComponent(lbResult)
                .addContainerGap(43, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

    private void btCalcActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        try {
            float a = Float.valueOf(tfA.getText());
            float b = Float.valueOf(tfB.getText());
            float c = Float.valueOf(tfC.getText());
            float delta = b * b - 4 * a * c;
            if (delta > 0) {
                float x1 = (float) ((-b + Math.sqrt(delta)) / (2 * a));
                float x2 = (float) ((-b - Math.sqrt(delta)) / (2 * a));
                String strResult = "x1 = " + String.valueOf(x1) + " ; x2 = " + String.valueOf(x2);
                lbResult.setText(strResult);
            }
            if (delta == 0) {
                float x = -b / (2 * a);
                lbResult.setText(String.valueOf(x));
            }
            if (delta < 0) {
                lbResult.setText("Vo nghiem");
            }
        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, "Error!");
            lbResult.setText("Error!");
        }
    }

    private void btClearActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        tfA.setText("");
        tfB.setText("");
        tfC.setText("");
        lbResult.setText("");
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* 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(Bac2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Bac2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Bac2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Bac2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Bac2().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JButton btCalc;
    private javax.swing.JButton btClear;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel lbResult;
    private javax.swing.JTextField tfA;
    private javax.swing.JTextField tfB;
    private javax.swing.JTextField tfC;
    // End of variables declaration
}