#MainFrame.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lesson07;

import javax.swing.table.DefaultTableModel;

/**
 *
 * @author Diep.Tran
 */
public class MainFrame extends javax.swing.JFrame {
    DefaultTableModel tableModel;
    
    /**
     * Creates new form MainFrame
     */
    public MainFrame() {
        initComponents();
        
        tableModel = (DefaultTableModel) jTable1.getModel();
    }

    /**
     * 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">//GEN-BEGIN:initComponents
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        fullnameTxt = new javax.swing.JTextField();
        emailTxt = new javax.swing.JTextField();
        jLabel2 = new javax.swing.JLabel();
        addressTxt = new javax.swing.JTextField();
        jLabel3 = new javax.swing.JLabel();
        saveBtn = new javax.swing.JButton();
        resetBtn = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("NHAP THONG TIN SINH VIEN");

        jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder("FORM NHAP"));

        jLabel1.setText("TEN: ");

        jLabel2.setText("EMAIL:");

        jLabel3.setText("ADDRESS: ");

        saveBtn.setText("SAVE");
        saveBtn.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                saveBtnActionPerformed(evt);
            }
        });

        resetBtn.setText("RESET");
        resetBtn.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                resetBtnActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(18, 18, 18)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addComponent(jLabel1)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(fullnameTxt, javax.swing.GroupLayout.PREFERRED_SIZE, 340, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addComponent(jLabel2)
                        .addGap(54, 54, 54)
                        .addComponent(emailTxt, javax.swing.GroupLayout.PREFERRED_SIZE, 340, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addComponent(jLabel3)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addComponent(saveBtn)
                                .addGap(18, 18, 18)
                                .addComponent(resetBtn))
                            .addComponent(addressTxt, javax.swing.GroupLayout.PREFERRED_SIZE, 340, javax.swing.GroupLayout.PREFERRED_SIZE))))
                .addContainerGap(32, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(fullnameTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(emailTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(addressTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(29, 29, 29)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(saveBtn)
                    .addComponent(resetBtn))
                .addContainerGap(14, Short.MAX_VALUE))
        );

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {

            },
            new String [] {
                "STT", "TEN", "EMAIL", "ADDRESS"
            }
        ) {
            boolean[] canEdit = new boolean [] {
                false, false, false, false
            };

            public boolean isCellEditable(int rowIndex, int columnIndex) {
                return canEdit [columnIndex];
            }
        });
        jScrollPane1.setViewportView(jTable1);
        if (jTable1.getColumnModel().getColumnCount() > 0) {
            jTable1.getColumnModel().getColumn(0).setResizable(false);
            jTable1.getColumnModel().getColumn(1).setResizable(false);
            jTable1.getColumnModel().getColumn(3).setResizable(false);
        }

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jScrollPane1)
                    .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 148, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void saveBtnActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_saveBtnActionPerformed
        // TODO add your handling code here:
        String fullname = fullnameTxt.getText();
        String email = emailTxt.getText();
        String address = addressTxt.getText();
        
        System.out.println("fullname = " + fullname + ", email = " + email + ", address = " + address);
        
        tableModel.addRow(new Object[] {tableModel.getRowCount() + 1, fullname, email, address});
    }//GEN-LAST:event_saveBtnActionPerformed

    private void resetBtnActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_resetBtnActionPerformed
        // TODO add your handling code here:
        fullnameTxt.setText("");
        emailTxt.setText("");
        addressTxt.setText("");
    }//GEN-LAST:event_resetBtnActionPerformed

    /**
     * @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(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainFrame.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 MainFrame().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JTextField addressTxt;
    private javax.swing.JTextField emailTxt;
    private javax.swing.JTextField fullnameTxt;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    private javax.swing.JButton resetBtn;
    private javax.swing.JButton saveBtn;
    // End of variables declaration//GEN-END:variables
}

#MainFrame.form

<?xml version="1.0" encoding="UTF-8" ?>

<Form version="1.3" maxVersion="1.9" type="org.netbeans.modules.form.forminfo.JFrameFormInfo">
  <Properties>
    <Property name="defaultCloseOperation" type="int" value="3"/>
    <Property name="title" type="java.lang.String" value="NHAP THONG TIN SINH VIEN"/>
  </Properties>
  <SyntheticProperties>
    <SyntheticProperty name="formSizePolicy" type="int" value="1"/>
    <SyntheticProperty name="generateCenter" type="boolean" value="false"/>
  </SyntheticProperties>
  <AuxValues>
    <AuxValue name="FormSettings_autoResourcing" type="java.lang.Integer" value="0"/>
    <AuxValue name="FormSettings_autoSetComponentName" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_generateFQN" type="java.lang.Boolean" value="true"/>
    <AuxValue name="FormSettings_generateMnemonicsCode" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_i18nAutoMode" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_layoutCodeTarget" type="java.lang.Integer" value="1"/>
    <AuxValue name="FormSettings_listenerGenerationStyle" type="java.lang.Integer" value="0"/>
    <AuxValue name="FormSettings_variablesLocal" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_variablesModifier" type="java.lang.Integer" value="2"/>
  </AuxValues>

  <Layout>
    <DimensionLayout dim="0">
      <Group type="103" groupAlignment="0" attributes="0">
          <Group type="102" alignment="0" attributes="0">
              <EmptySpace max="-2" attributes="0"/>
              <Group type="103" groupAlignment="0" attributes="0">
                  <Component id="jScrollPane1" max="32767" attributes="0"/>
                  <Component id="jPanel1" max="32767" attributes="0"/>
              </Group>
              <EmptySpace max="-2" attributes="0"/>
          </Group>
      </Group>
    </DimensionLayout>
    <DimensionLayout dim="1">
      <Group type="103" groupAlignment="0" attributes="0">
          <Group type="102" alignment="0" attributes="0">
              <EmptySpace max="-2" attributes="0"/>
              <Component id="jPanel1" min="-2" max="-2" attributes="0"/>
              <EmptySpace max="-2" attributes="0"/>
              <Component id="jScrollPane1" min="-2" pref="148" max="-2" attributes="0"/>
              <EmptySpace max="32767" attributes="0"/>
          </Group>
      </Group>
    </DimensionLayout>
  </Layout>
  <SubComponents>
    <Container class="javax.swing.JPanel" name="jPanel1">
      <Properties>
        <Property name="border" type="javax.swing.border.Border" editor="org.netbeans.modules.form.editors2.BorderEditor">
          <Border info="org.netbeans.modules.form.compat2.border.TitledBorderInfo">
            <TitledBorder title="FORM NHAP"/>
          </Border>
        </Property>
      </Properties>

      <Layout>
        <DimensionLayout dim="0">
          <Group type="103" groupAlignment="0" attributes="0">
              <Group type="102" alignment="0" attributes="0">
                  <EmptySpace min="-2" pref="18" max="-2" attributes="0"/>
                  <Group type="103" groupAlignment="0" max="-2" attributes="0">
                      <Group type="102" alignment="1" attributes="0">
                          <Component id="jLabel1" min="-2" max="-2" attributes="0"/>
                          <EmptySpace max="32767" attributes="0"/>
                          <Component id="fullnameTxt" min="-2" pref="340" max="-2" attributes="0"/>
                      </Group>
                      <Group type="102" alignment="1" attributes="0">
                          <Component id="jLabel2" min="-2" max="-2" attributes="0"/>
                          <EmptySpace min="-2" pref="54" max="-2" attributes="0"/>
                          <Component id="emailTxt" min="-2" pref="340" max="-2" attributes="0"/>
                      </Group>
                      <Group type="102" alignment="1" attributes="0">
                          <Component id="jLabel3" min="-2" max="-2" attributes="0"/>
                          <EmptySpace max="32767" attributes="0"/>
                          <Group type="103" groupAlignment="0" attributes="0">
                              <Group type="102" attributes="0">
                                  <Component id="saveBtn" min="-2" max="-2" attributes="0"/>
                                  <EmptySpace type="separate" max="-2" attributes="0"/>
                                  <Component id="resetBtn" min="-2" max="-2" attributes="0"/>
                              </Group>
                              <Component id="addressTxt" min="-2" pref="340" max="-2" attributes="0"/>
                          </Group>
                      </Group>
                  </Group>
                  <EmptySpace pref="32" max="32767" attributes="0"/>
              </Group>
          </Group>
        </DimensionLayout>
        <DimensionLayout dim="1">
          <Group type="103" groupAlignment="0" attributes="0">
              <Group type="102" alignment="0" attributes="0">
                  <EmptySpace max="-2" attributes="0"/>
                  <Group type="103" groupAlignment="3" attributes="0">
                      <Component id="jLabel1" alignment="3" min="-2" max="-2" attributes="0"/>
                      <Component id="fullnameTxt" alignment="3" min="-2" max="-2" attributes="0"/>
                  </Group>
                  <EmptySpace type="separate" max="-2" attributes="0"/>
                  <Group type="103" groupAlignment="3" attributes="0">
                      <Component id="jLabel2" alignment="3" min="-2" max="-2" attributes="0"/>
                      <Component id="emailTxt" alignment="3" min="-2" max="-2" attributes="0"/>
                  </Group>
                  <EmptySpace type="separate" max="-2" attributes="0"/>
                  <Group type="103" groupAlignment="3" attributes="0">
                      <Component id="jLabel3" alignment="3" min="-2" max="-2" attributes="0"/>
                      <Component id="addressTxt" alignment="3" min="-2" max="-2" attributes="0"/>
                  </Group>
                  <EmptySpace min="-2" pref="29" max="-2" attributes="0"/>
                  <Group type="103" groupAlignment="3" attributes="0">
                      <Component id="saveBtn" alignment="3" min="-2" max="-2" attributes="0"/>
                      <Component id="resetBtn" alignment="3" min="-2" max="-2" attributes="0"/>
                  </Group>
                  <EmptySpace pref="14" max="32767" attributes="0"/>
              </Group>
          </Group>
        </DimensionLayout>
      </Layout>
      <SubComponents>
        <Component class="javax.swing.JLabel" name="jLabel1">
          <Properties>
            <Property name="text" type="java.lang.String" value="TEN: "/>
          </Properties>
        </Component>
        <Component class="javax.swing.JTextField" name="fullnameTxt">
        </Component>
        <Component class="javax.swing.JTextField" name="emailTxt">
        </Component>
        <Component class="javax.swing.JLabel" name="jLabel2">
          <Properties>
            <Property name="text" type="java.lang.String" value="EMAIL:"/>
          </Properties>
        </Component>
        <Component class="javax.swing.JTextField" name="addressTxt">
        </Component>
        <Component class="javax.swing.JLabel" name="jLabel3">
          <Properties>
            <Property name="text" type="java.lang.String" value="ADDRESS: "/>
          </Properties>
        </Component>
        <Component class="javax.swing.JButton" name="saveBtn">
          <Properties>
            <Property name="text" type="java.lang.String" value="SAVE"/>
          </Properties>
          <Events>
            <EventHandler event="actionPerformed" listener="java.awt.event.ActionListener" parameters="java.awt.event.ActionEvent" handler="saveBtnActionPerformed"/>
          </Events>
        </Component>
        <Component class="javax.swing.JButton" name="resetBtn">
          <Properties>
            <Property name="text" type="java.lang.String" value="RESET"/>
          </Properties>
          <Events>
            <EventHandler event="actionPerformed" listener="java.awt.event.ActionListener" parameters="java.awt.event.ActionEvent" handler="resetBtnActionPerformed"/>
          </Events>
        </Component>
      </SubComponents>
    </Container>
    <Container class="javax.swing.JScrollPane" name="jScrollPane1">
      <AuxValues>
        <AuxValue name="autoScrollPane" type="java.lang.Boolean" value="true"/>
      </AuxValues>

      <Layout class="org.netbeans.modules.form.compat2.layouts.support.JScrollPaneSupportLayout"/>
      <SubComponents>
        <Component class="javax.swing.JTable" name="jTable1">
          <Properties>
            <Property name="model" type="javax.swing.table.TableModel" editor="org.netbeans.modules.form.editors2.TableModelEditor">
              <Table columnCount="4" rowCount="0">
                <Column editable="false" title="STT" type="java.lang.Object"/>
                <Column editable="false" title="TEN" type="java.lang.Object"/>
                <Column editable="false" title="EMAIL" type="java.lang.Object"/>
                <Column editable="false" title="ADDRESS" type="java.lang.Object"/>
              </Table>
            </Property>
            <Property name="columnModel" type="javax.swing.table.TableColumnModel" editor="org.netbeans.modules.form.editors2.TableColumnModelEditor">
              <TableColumnModel selectionModel="0">
                <Column maxWidth="-1" minWidth="-1" prefWidth="-1" resizable="false">
                  <Title/>
                  <Editor/>
                  <Renderer/>
                </Column>
                <Column maxWidth="-1" minWidth="-1" prefWidth="-1" resizable="false">
                  <Title/>
                  <Editor/>
                  <Renderer/>
                </Column>
                <Column maxWidth="-1" minWidth="-1" prefWidth="-1" resizable="true">
                  <Title/>
                  <Editor/>
                  <Renderer/>
                </Column>
                <Column maxWidth="-1" minWidth="-1" prefWidth="-1" resizable="false">
                  <Title/>
                  <Editor/>
                  <Renderer/>
                </Column>
              </TableColumnModel>
            </Property>
            <Property name="tableHeader" type="javax.swing.table.JTableHeader" editor="org.netbeans.modules.form.editors2.JTableHeaderEditor">
              <TableHeader reorderingAllowed="true" resizingAllowed="true"/>
            </Property>
          </Properties>
        </Component>
      </SubComponents>
    </Container>
  </SubComponents>
</Form>

#Main.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lesson07;

import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Diep.Tran
 */
public class Main {
    public static void main(String[] args) {
        //Logic -> error
        //Chia cho 0, Out of index
        Scanner scan = new Scanner(System.in);
        
        System.out.println("Nhap x = ");
        int x = scan.nextInt();
        
        System.out.println("Nhap y = ");
        int y = scan.nextInt();
        
        //fix 1 -> luon luon ap dung
        /**if(y == 0) {
            System.out.println("Ko dc phep chia cho 0");
        } else {
            int s = x / y;
            System.out.println("s = " + s);
        }*/
        
        //fix 2 -> bat error bang khoi code try catch finally
        /**
        try {
            //Noi dat code -> nghi van dan toi exception (crash) chuong trinh
            int s = x / y;
            System.out.println("s = " + s);
            
            int[] t = new int[3];
            t[0] = 9;
            t[6] = 10;
        } catch(ArithmeticException e) {
//            e.printStackTrace();
            System.out.println("Loi phep toan ...");
        } catch(ArrayIndexOutOfBoundsException e) {
//            e.printStackTrace();
            System.out.println("Out of index ...");
        } catch(Exception e) {
            //Khi code -> exception -> thuc thi khoi code o day
            System.out.println("Exception ...");
        } finally {
            //Code -> luon dc goi sau khi ket thuc try va catch
            System.out.println("Finally ...");
        }
        */
        try {
            float s = Calculator.chia(x, y);
            System.out.println("s = " + s);
        } catch (CalculatorException ex) {
            ex.showMsg();
        }
        
        try {
            float s2 = Calculator.chia2(x, y);
            System.out.println("s = " + s2);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        
        //Keys datetime
        //convert datetime to string java -> Hien thi + insert/update database
        //convert string to datetime java -> database -> lap trinh -> compare
        //add n hours to a date in java
        //https://stackoverflow.com/questions/3581258/adding-n-hours-to-a-date-in-java
        
    }
}

#CalculatorException.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lesson07;

/**
 *
 * @author Diep.Tran
 */
public class CalculatorException extends Exception{
    float x, y;

    public CalculatorException() {
    }

    public CalculatorException(float x, float y, String msg) {
        super(msg);
        this.x = x;
        this.y = y;
    }
    
    public void showMsg() {
        System.out.println("x = " + x + ", y = " + y + ", msg = " + getMessage());
    }
}

#Calculator.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lesson07;

/**
 *
 * @author Diep.Tran
 */
public class Calculator {
    public static float cong(float x, float y) {
        return x + y;
    }
    
    public static float tru(float x, float y) {
        return x - y;
    }
    
    public static float nhan(float x, float y) {
        return x * y;
    }
    
    public static float chia(float x, float y) throws CalculatorException {
        if(y == 0) {
//            System.out.println("Khong dc phep chia cho 0");
//            return 0;
            //Nen lam cho chuong trinh bi crash -> exception
            throw new CalculatorException(x, y, "Devide by Zero");
        }
        return x / y;
    }
    
    public static float chia2(float x, float y) {
        if(y == 0) {
            throw new ArithmeticException("Devide by Zero!!!");
        }
        return x / y;
    }
    
    public static float chia3(float x, float y) throws Exception {
        if(y == 0) {
            throw new Exception("Devide by Zero!!!");
        }
        return x / y;
    }
}