FileOutputStream Example in Java

Whenever data needs to be written into file dont just write using fileoutputstream. Use BufferedOutputStream

to increase the efficiency and reduce the performance complexity.

#Whenever data is written into file using any outputstream we need to flush the stream and close the stream properly. Otherwise it will lead to memory leak and data writing gets failed. 



import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;

/**
 *
 * @author Saravanan K
 */
public class FileOutputStreamDemo{
   

    public static void createAndWriteIntoFile(String fileLocation,String fileName,String content)
    {
        if(fileLocation!=null&&fileName!=null)
        {
            FileOutputStream fos = null;
            try {
                String file = fileLocation+File.separator+fileName;
                fos = new FileOutputStream(file);
                BufferedOutputStream bos = new BufferedOutputStream(fos);
                bos.write(content.getBytes());
                bos.flush();
                bos.close();
            } catch (FileNotFoundException ex) {
                System.out.println(""+ex.toString());
            } catch (IOException ex) {
                System.out.println(""+ex.toString());            } 
            finally {
                try {
                    fos.close();
                } catch (IOException ex) {
                    System.out.println(""+ex.toString());
                }
            }
        } else {
            System.out.println("Sorry.Filename cannot be empty...");
        }
        System.out.println("File wrote success");
    }
    public static void main(String[] args) {
       
        String location="K:";
        String fileName = "TestFile.doc";
        String content = "Hi this is FileOutputStreamDemo...";
          
        createAndWriteIntoFile(location, fileName, content);
    }
}

Remove Numbers in String - Java Program

public String removeNumbersInString(String str) {

        String temp = "";

        String regexp = "^[0-9]";

        Pattern pattern = Pattern.compile(regexp);

        Matcher matcher;

        if(!str.isEmpty()){

        for (int i = 0; i < str.length(); i++) {

            matcher = pattern.matcher(str.charAt(i) + "");

            if (!matcher.matches()) {

                temp = temp + str.charAt(i) + "";

            }

        }}

        System.out.println("" + temp);

        return temp;

    }

Remove String in Numbers-Java Program

public String removeStringInNumbers(String str) {

        String temp = "";

        String regexp = "^[a-zA-Z]";

        Pattern pattern = Pattern.compile(regexp);

        Matcher matcher;

        if(!str.isEmpty()){

        for (int i = 0; i < str.length(); i++) {

            matcher = pattern.matcher(str.charAt(i) + "");

            if (!matcher.matches()) {

                temp = temp + str.charAt(i) + "";

            }

        }}

        System.out.println("" + temp);

        return temp;

    }

Write an example that counts the number of times a particular character, such as e, appears in a file. The character can be specified at the command line.

import java.io.BufferedInputStream;
import java.io.FileInputStream;

class GetOccurrences{
    public static void main(String args[])
    {
        try{
            FileInputStream fis=new FileInputStream("C:\\Users\\SAN-MCA-ME-MTECH-MS\\Documents\\SAN\\Temp.txt");
            BufferedInputStream bis=new BufferedInputStream(fis);
                    
            int i;
            int occurs=0;
            
            while((i=bis.read())!=-1)
            {
                char a=(char)i;
                
                if(a==args[0].charAt(0))
                {
                 occurs++;
                }
            }
            System.out.println("Letter e  is "+occurs+" of times repeated in the file");
        }catch(Exception ex)
        {
            System.out.println(ex.getMessage());
        }
    }
}

Java Connect to Oracle XE Database

 

In order to connect to oracle  database you need to add ojdbc14.jar file in your eclipse project as a external jar file.... Download from web.

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class OracleConnect {

    /**
     * @param args
     */
    public static void main(String[] args) throws IOException{
        // TODO Auto-generated method stub
        try
        {
        Class.forName("oracle.jdbc.driver.OracleDriver");
        Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","saravanan","saravanan");
        System.out.println("Connected Successfully To Oracle");
        Statement stmt;
        ResultSet rs;
        stmt=con.createStatement();
        rs=stmt.executeQuery("select * from saran");
        
       while(rs.next())
       {
            System.out.println(rs.getString("empname")+"--"+rs.getInt("salary"));
       }
        
        
        }
        catch(Exception ex)
        {
        ex.printStackTrace();
        }

    }

}

Simple java program for connecting to DATABASE(mysql)

In order to connect to database you need to add mysql-connector-java-5.1.22.jar file in your eclipse project as a external jar file....

import java.sql.Connection;

import java.sql.Driver;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;



public class SqlSample {



    /**

     * @param args

     * @throws ClassNotFoundException 

     * @throws IllegalAccessException 

     * @throws InstantiationException 

     * @throws SQLException 

     */

    public static void main(String[] args) throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {

        // TODO Auto-generated method stub

        Connection con;

        Class.forName("com.mysql.jdbc.Driver");

        con = DriverManager.getConnection("jdbc:mysql://localhost/saran","root","root");

        Statement stmt;

        ResultSet rs;

        stmt=con.createStatement();

        rs=stmt.executeQuery("select * from employee;");

        

        while(rs.next())

        {

            System.out.println(rs.getString("empname")+rs.getInt("salary"));

        }

    }



}

Servlet Program for Retrieving data from Table

In order to connect to database you need to add mysql-connector-java-5.1.22.jar file in your eclipse project as a external jar file.... 

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;



/**

 * Servlet implementation class HelloServlet

 */

import java.io.*;



import javax.servlet.*;

import javax.servlet.http.*;



import java.sql.*;



public

    class HelloServlet extends HttpServlet {

    

    public void doGet (HttpServletRequest req, HttpServletResponse res)

        throws ServletException, IOException {

        res.setContentType("text/html");

        

        PrintWriter out=res.getWriter();

        out.println("<html>");

        out.println("<head><title>Students List</title></head>");

        out.println("<body>");

        

        try {

        // The newInstance() call is a work around for some

        // broken Java implementations

        

        Class.forName("com.mysql.jdbc.Driver").newInstance();

        }

        catch (Exception E) {

        out.println("Unable to load driver.");

        E.printStackTrace();

        }

        

        out.println("<br><center><p style=color:purple;font-size:30px;>STUDENTS DATABASE</p></center><hr>");

        

        try {

        Connection Conn = 

            DriverManager.getConnection("jdbc:mysql://localhost/saran","root","root");

            

        // Do something with the Connection

        Statement Stmt = Conn.createStatement();

        ResultSet RS = Stmt.executeQuery("SELECT * from student");

        out.println("<center><table border='1' style=color:purple;font-size:20px;><th>Name</th><th>Area</th><th>Course</th>");

        while (RS.next()) {

            out.println("<tr><td>"+RS.getString("name")+"<td>"+RS.getString("area")+"<td>"+RS.getString("course")+"</td></tr>");

            

        }

        out.println("</table></center>");

        out.println("<center><form action='index.htm'><input type='submit' value='Home'></form></center>");

        // Clean up after ourselves

        RS.close();

        Stmt.close();

        Conn.close();

        

        }

        catch (SQLException E) {

        

        }

        

        

        out.println("</body></html>");

    }

    

    }