Learn Android Apps Development Tutorial: Begining to Advance

First program in java

Last Updated on: 6th Feb 2025 12:25:18 PM

class FirstProgram{  
    public static void main(String args[]){  
     System.out.println("Hello Java");  
    }  
}

This is our first program of java which will print "Hello Java" in console screen.

Save the above file as FirstProgram.java.

How To Compile :

Javac FirstProgram.java

How to Run:

java FirstProgram

========================================================================

Aggregation in java

Address.java

public class Address {
String city,state,country;
Address(String city, String state,String country)
{
    this.city=city;
    this.state=state;
    this.country=country;
}
}

Student,java

/**
 * Student
 */
public class Student {
    int roll;
    String name;
    Address address;

    Student(int roll, String name, Address address) {
        this.roll = roll;
        this.name = name;
        this.address = address;

    }

    void dispaly() {
        System.out.println("My name is " + this.name + " Roll is " + this.roll);
        System.out.println("City :" + address.city + " State : " + address.state + 
      " Country : " + address.country);
    }

    public static void main(String[] args) {

        Address a = new Address("Mumbai", "Maharastra", "india");
        Address a1 = new Address("Pune", "Maharastra", "india");
        Student s = new Student(101, "sandip", a);
        Student s1 = new Student(102, "Amit", a1);
        s.dispaly();
        s1.dispaly();

    }
}

JDBC

import java.sql.*;  // set path// :     set path=C:Program FilesJavajdk-17.0.2in
class Database{    // run javac -cp mysql-connector-java-8.0.29.jar;. Database.java
public static void main(String args[]){  
try{  
Class.forName("com.mysql.cj.jdbc.Driver");  
//Connection con=DriverManager.getConnection("jdbc:mysql://localhost:4306/mydata","root","sandip@123");//xamp port   
Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/sandip","root","sandip@1234");  //mysql port
Statement stmt=con.createStatement();  
ResultSet rs=stmt.executeQuery("select * from register");  
while(rs.next())  
System.out.println(rs.getInt(1)+"  "+rs.getString(2)+"  "+rs.getString(3));  
con.close();  
}catch(Exception e){ System.out.println(e);}  
}  
}

insertdata

try ( PrintWriter out = response.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            
            String name = request.getParameter("name");	
	    String password = request.getParameter("password");
	    String email = request.getParameter("email");
	    String number = request.getParameter("number");
	    String address = request.getParameter("address");
            
            
           
	
            Class.forName("com.mysql.jdbc.Driver");
		
		// get the connection
		Connection co = DriverManager.getConnection("jdbc:mysql://localhost:3306/bhaskar","root","sandip@123");
		// get the PS
		//PreparedStatement ps = co.prepareStatement("insert into employee values(?,?,?,?,?)");
                 PreparedStatement ps =    co.prepareStatement("INSERT INTO employee (name,password,email,number,address) values (?, ? , ?, ?, ?)");
		// provide values in place of ? mark
		ps.setString(1, name);
                ps.setString(2, password);
		ps.setString(3, email);
                ps.setString(4, number);
		ps.setString(5, address); 
		
		// execute the sql statement
		ps.executeUpdate();
		
		// get print writer to show the data on browser
		 
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet MyServlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<center>");
            out.println("<font style="font-size: 30px" color="green">Account is created</font>");
            // this is used to include the html page in servlet
            request.getRequestDispatcher("index.html").include(request, response);  
            out.println("<a href="Login.html">click here for login</a>");
            out.println("</center>");
            //out.println("<h1>My Name : " + name+"<br> Password : "+password+"<br> Email : "+email+"<br> Number : "+number+ "<br>Address : " +address+"</h1>");
            out.println("</body>");
            out.println("</html>");
            // load driver class
		// show a link on web browser at the client size
                
               
          
      
            
            
	
        }catch (Exception e) 
	{
		// cause and line no of exception will be printed on server console
		e.printStackTrace();
	}

fetch data from database

   Statement st;
            ResultSet rs;
            Class.forName("com.mysql.jdbc.Driver");
            Connection con=DriverManager.getConnection("jdbc:mysql://localhost:4306/mydata","root","sandip@123");
            st=con.createStatement();
            String query = "select * from student";
            rs=st.executeQuery(query);
            
          
            
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet ViewRecord</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<center>");
              
            out.println("<table cellspacing="0" width ="500px" border="1">"); // use single inverted
            out.println("<tr>");
            out.println("<td>   Name :</td>");
            out.println("<td>   Address :</td>");
            out.println("<td>   Update:</td>");
            out.println("<td>   Delete:</td>");
            out.println("</tr>");
              while(rs.next())
            {
            
            String name=rs.getString("name");
            String address=rs.getString("address");
            
          
               out.println("<tr>");
               out.println("<td>"+name+"</td>");
               out.println("<td>"+address+"</td>");
               out.println("<td> <a href="Edit?name="+rs.getString("name")+"">Edit</a> </td>");// use single inverted comma
               out.println("<td> <a href="Delete?name="+rs.getString("name")+"">Delete</a> </td>");  //use single inverted
   out.println("<td> <a href='Edit?id="+rs.getString("id")+"'>Edit</a> </td>");
             out.println("<td> <a href='Delete?id="+rs.getString("id")+"'>Delete</a> </td>");
          
               out.println("</tr>");
          }
              out.println("</table>");
              out.println("</center>");
            out.println("</body>");
            out.println("</html>");
        }

Delete

 
            //String emp_id=request.getParameter("id");
            Connection cn1;
            Class.forName("com.mysql.cj.jdbc.Driver");
            cn1=DriverManager.getConnection("jdbc:mysql://localhost:3306/bhaskar","root","sandip@123");
            PreparedStatement statement = cn1.prepareStatement("delete from employee WHERE id = ? ");    //ps.setString(1, (String) jTable1. getValueAt(x, 0));  
            
            statement.setString(1,request.getParameter("id"));
             
            int row = statement.executeUpdate();
           
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet UpdateServlet</title>");            
            out.println("</head>");
            out.println("<body>");
             if (row > 0) 
            {
            
           out.println("<h1><font color='green'>Sucessfully deleted</font></h1>");
          
            
            }
            
            out.println("</body>");
            out.println("</html>");
        }
        catch (Exception e) 
	{
		// cause and line no of exception will be printed on server console
		e.printStackTrace();
	}

Edit

  /* TODO output your page here. You may use following sample code. */
            String eid =request.getParameter("id");
            Statement st1;
            Connection cn;
            ResultSet rs;
            Class.forName("com.mysql.cj.jdbc.Driver");
            cn=DriverManager.getConnection("jdbc:mysql://localhost:3306/bhaskar","root","sandip@123");
            st1=cn.createStatement();
            String p="select * from employee where id ="+eid+" ";
            rs=st1.executeQuery(p);
                
            
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet Edit</title>");            
            out.println("</head>");
            out.println("<body>");
             while (rs.next())
                {
                    
             out.println("<form method=\"POST\" action=\"UpdateServlet\">");
             out.println("<center><table width='500px'>");
             out.println("<tr>  <td><input type ='hidden' name='id' value='"+rs.getString("id")+"'></td>");
             out.println("<tr><td> Name </td>  <td><input type ='text' name= 'name' value='"+rs.getString("name")+"'></td></tr>");
             out.println("<tr><td> password : </td>  <td><input type ='text' name='password'value='"+rs.getString("password")+"'></td></tr");
             out.println("<tr><td> Email : </td>  <td><input type ='text' name ='email' value='"+rs.getString("email")+"'></td></tr");
             out.println("<tr><td> Mobile No : </td>  <td><input type ='text' name ='number' value='"+rs.getString("number")+"'></td></tr");       
             out.println("<tr><td> Address </td>  <td><input type ='text' name='address' value='"+rs.getString("address")+"'></td></tr");
             out.println("<tr><td></td><td><br><br><input type ='submit' value='Update'></td></tr>");
             out.println("</table></center>");
             out.println("</form>");
             out.println("</tr>");
                }
            out.println("</body>");
            out.println("</html>");
               st1.close();
               cn.close();
        }
        catch(Exception e)
        {
            System.out.println(e.getMessage());
        
        }

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