How to get data from database to jcombobox in java swing NetBeans

Connect JAVA with MYSQL database | insert Data into Table Example Source Code

/* action perform event for insert data into table
 Database : student_info
Table : class5
root username of mysql db
mysql@123 is a password of db

*/
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        //first get rollno and name enter by user
        String rollNo = txtRollNo.getText();
        String Name = txtName.getText();
       
        //convert roll no into integer
        int RNo = Integer.parseInt(rollNo);
        //connection
        try{
            //open connection
            Class.forName("com.mysql.jdbc.Driver");
           
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/student_info","root","mysql@123");
            //here student_info is a database
            //root is username of mysql and mysql@123 is a password
           
            //for insert data into table
            Statement stm = con.createStatement();
           
            String sql = "INSERT INTO CLASS5  VALUES("+RNo+",'"+Name+"')";
            //class5 in above queary is a table
            //EXECUTE STATEMENT
            stm.executeUpdate(sql); //here insert query apply
           
            //display message of record inserted
            JOptionPane.showMessageDialog(this, "student Record Inserted");
            txtName.setText("");
            txtRollNo.setText("");
            //close connection
            con.close();
           
           
        }catch(Exception e){
            System.out.println(e.getMessage());
        }
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
       
    }                                        

Game Source Netbeans java

package oddevengame;

import java.util.Random;
import javax.swing.JOptionPane;

/**
 *
 * @author Sahaj
 */
public class ODDEven extends javax.swing.JFrame {
        static int score = 0; // score each corrent question add 1
        static int count = 0; // number of  question out of 10
       
        //generate random number for each question(number)
        Random r = new Random();
        int randomNum;
       
    /**
     * Creates new form ODDEven
     */
    public ODDEven() {
        initComponents();
        //first time generate random
        randomNum = r.nextInt(100);
        lblNumber.setText(String.valueOf(randomNum));
    }

    /**
     * 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() {

        lblNumber = new javax.swing.JLabel();
        btnOdd = new javax.swing.JButton();
        btnEven = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();
        lblScore = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        lblNumber.setFont(new java.awt.Font("Tahoma", 1, 48)); // NOI18N
        lblNumber.setForeground(new java.awt.Color(255, 0, 51));

        btnOdd.setFont(new java.awt.Font("Tahoma", 1, 24)); // NOI18N
        btnOdd.setText("ODD");
        btnOdd.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnOddActionPerformed(evt);
            }
        });

        btnEven.setFont(new java.awt.Font("Tahoma", 1, 24)); // NOI18N
        btnEven.setText("EVEN");
        btnEven.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnEvenActionPerformed(evt);
            }
        });

        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 24)); // NOI18N
        jLabel1.setText("SCORE");

        lblScore.setFont(new java.awt.Font("Tahoma", 1, 24)); // NOI18N

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(51, 51, 51)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addComponent(btnOdd, javax.swing.GroupLayout.DEFAULT_SIZE, 92, Short.MAX_VALUE)
                            .addComponent(jLabel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                        .addGap(34, 34, 34)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(lblScore, javax.swing.GroupLayout.PREFERRED_SIZE, 122, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(btnEven, javax.swing.GroupLayout.PREFERRED_SIZE, 108, javax.swing.GroupLayout.PREFERRED_SIZE)))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(122, 122, 122)
                        .addComponent(lblNumber, javax.swing.GroupLayout.PREFERRED_SIZE, 95, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap(40, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(24, 24, 24)
                .addComponent(lblNumber, javax.swing.GroupLayout.PREFERRED_SIZE, 48, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(btnOdd, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(btnEven, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addGap(47, 47, 47)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 30, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(lblScore, javax.swing.GroupLayout.PREFERRED_SIZE, 36, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(41, Short.MAX_VALUE))
        );

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

    private void btnOddActionPerformed(java.awt.event.ActionEvent evt) {                                     
        // TODO add your handling code here:
        //odd operation
        count = count+1; //each button click count question add 1 out of 10
        int num = Integer.parseInt(lblNumber.getText());  //lblnumber is random num and convert to int for odd even operation
        if(count==10){
            //when counter reach last question(number)
            //than it calculate for last number
            if(num%2!=0){
                // number corret add score
                score = score+1;
                lblScore.setText(String.valueOf(score)); //set value of score when answer correct
                randomNum = r.nextInt(100); // random number generate for next question number
               
            }else{
                //if not odd number
                randomNum = r.nextInt(100);
                lblNumber.setText(String.valueOf(randomNum)); //set randomnumber
                             
            }
           
            //result display on 10th question
            JOptionPane.showMessageDialog(this, "Your score is: "+score+"/10");
            //reset values after score
            count=0;
            score =0;
            lblScore.setText("");
            randomNum = r.nextInt(100);
            lblNumber.setText(String.valueOf(randomNum));
           
        }else{
            // if number not reach 10th qestion ( for 1 to 9 )
            if(num%2!=0){
                score = score+1;
                lblScore.setText(String.valueOf(score)); //set score value
                //generate random number for next question
                randomNum = r.nextInt(100);
                lblNumber.setText(String.valueOf(randomNum));
            }else{
                //if not odd than generate random for next
                randomNum = r.nextInt(100);
                lblNumber.setText(String.valueOf(randomNum));
            }
        }
       
       
       
    }                                     

    private void btnEvenActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        // for even do opposite
        //paste here and change
       
        count = count+1; //each button click count question add 1 out of 10
        int num = Integer.parseInt(lblNumber.getText());  //lblnumber is random num and convert to int for odd even operation
        if(count==10){
            //when counter reach last question(number)
            //than it calculate for last number
            if(num%2==0){
                // number corret add score
                score = score+1;
                lblScore.setText(String.valueOf(score)); //set value of score when answer correct
                randomNum = r.nextInt(100); // random number generate for next question number
               
            }else{
                //if not odd number
                randomNum = r.nextInt(100);
                lblNumber.setText(String.valueOf(randomNum)); //set randomnumber
                             
            }
           
            //result display on 10th question
            JOptionPane.showMessageDialog(this, "Your score is: "+score+"/10");
            //reset values after score
            count=0;
            score =0;
            lblScore.setText("");
            randomNum = r.nextInt(100);
            lblNumber.setText(String.valueOf(randomNum));
           
        }else{
            // if number not reach 10th qestion ( for 1 to 9 )
            if(num%2==0){
                score = score+1;
                lblScore.setText(String.valueOf(score)); //set score value
                //generate random number for next question
                randomNum = r.nextInt(100);
                lblNumber.setText(String.valueOf(randomNum));
            }else{
                //if not odd than generate random for next
                randomNum = r.nextInt(100);
                lblNumber.setText(String.valueOf(randomNum));
            }
        }
       
       
    }                                     

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

    // Variables declaration - do not modify                   
    private javax.swing.JButton btnEven;
    private javax.swing.JButton btnOdd;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel lblNumber;
    private javax.swing.JLabel lblScore;
    // End of variables declaration                 
}

Constructor Overloading Example in java

/* program of constructor overloading in java */

class addition{
//constructor declaration two argument
addition(int a, int b){
// perform sum of two numbers
int sum = a+b;
System.out.println("sum of two numbers :"+sum);

}

//three argument constructor
addition(int a, int b, int c){
// perform sum of three numbers
int sum = a+b+c;
System.out.println("sum of three numbers :"+sum);

}
public static void main(String args[]){
addition obj = new addition(2,2); //called two argument constructor
addition obj1 = new addition(3,3,3); // called three argument constructor

}
}

How to Get First and Last word from String using Java

/* java program to get first and last word of a string */

class wordDisplay{
public static void main(String args[]){

String str = "Object Oriented Protramming" ;

//get first word
int firstSpacePosition = str.indexOf(" ");

String firstWord = str.substring(0,firstSpacePosition); // Object

//get last word

String lastWord = str.substring(str.lastIndexOf(" ")+1); //Programming

//print
System.out.println("first word : "+firstWord);
System.out.println("Last word: "+lastWord);
}
}

java program to get first and last character of a string

/* java program to get first and last character of a string */

 class PositionDemo{
public static void main(String args[]){

String str = "123456789" ;

//get First character
char first = str.charAt(0);

//get Last character
char last = str.charAt(str.length()-1);  //get last character

System.out.println("First charcater : "+first);
System.out.println("Last charcter :"+last);

}
 }

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