This document contains code for a login system program with the following functionality: 1. It allows users to register with a username and password, which are encrypted and stored in a database. 2. Users can log in by entering their username and password, which are decrypted and validated against the database. 3. Registered users can be viewed by decrypting the usernames retrieved from the database. 4. The database contents can be displayed. The program uses a switch case to prompt the user for their choice of these options and take the appropriate action.

1. Assignment-1
package R100212049.AbhinavKhurana.ques1;
import java.io.*;
import java.sql.*;
import java.util.*;
public class q1 {
public static void main(String[] args) throws Exception {
String h = null;
StringBuffer sb;
Class.forName("com.mysql.jdbc.Driver");
Properties prop=new Properties();
String url="jdbc:mysql://localhost:3306/db1";
prop.setProperty("user", "root");
prop.setProperty("password", "admin");
Connection conn= DriverManager.getConnection(url, prop);
Statement stmt=conn.createStatement();
// stmt.executeUpdate("create table INFO(name varchar(30),pass varchar(30))");
do{
System.out.println("LOGIN SYSTEM");
System.out.println("Enter your choice");
System.out.println("1.Register");
System.out.println("2.Login");
System.out.println("3.View Users");
System.out.println("4.Show Database State");
Scanner sc= new Scanner(System.in);
int i=sc.nextInt();
switch (i) {
case 1:
sb=new StringBuffer();
System.out.println("Enter username");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String fname=br.readLine();
for(int l=0;l<fname.length();l++)
{
char ch=fname.charAt(l);
ch=(char) (ch+1);
sb.append(ch);
}
fname=new String(sb);

2. System.out.println("Enter the password");
String pwd=br.readLine();
System.out.println("ReEnter your password ");
String rpwd=br.readLine();
sb=new StringBuffer();
if(pwd.equals(rpwd))
{
for(int l=0;l<pwd.length();l++)
{
char r=pwd.charAt(l);
r=(char)(r+1);
sb.append(r);
}
pwd=new String(sb);
System.out.println("Account Sucessfully created");
PreparedStatement pst= conn.prepareStatement("insert into INFO
values(?,?)");
pst.setString(1,fname);
pst.setString(2,pwd);
pst.executeUpdate();
}
else
{
System.out.println("Password doesn't match");
}
break;
case 2:
BufferedReader b=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter Username");
String lname=b.readLine();
System.out.println("Enter Password");
String lpwd=b.readLine();
sb=new StringBuffer();
for(int l=0;l<lname.length();l++)
{
char ch1=lname.charAt(l);
ch1=(char) (ch1+1);
sb.append(ch1);
}
lname=new String(sb);
PreparedStatement st=conn.prepareStatement("select pass from INFO where
name=?");
st.setString(1,lname);
ResultSet rs=st.executeQuery();
sb=new StringBuffer();
while(rs.next())
{
h=rs.getString(1);
for(int l=0;l<h.length();l++)
{

3. char r=h.charAt(l);
r=(char)(r-1);
sb.append(r);
}
h=new String(sb);
if(h.equals(lpwd))
{
System.out.println("Login successfully");
}
else
{
System.out.println("Wrong Password");
}
}
break;
case 3:
ResultSet ro=stmt.executeQuery("select name from INFO");
while(ro.next())
{
sb=new StringBuffer();
h=ro.getString(1);
for(int m=0;m<h.length();m++)
{
char r=h.charAt(m);
r=(char)(r-1);
sb.append(r);
}
h=new String(sb);
System.out.println(h);
}
break;
case 4:
ResultSet r=stmt.executeQuery("select * from INFO");
while(r.next())
{
System.out.println(r.getString(1)+" "+r.getString(2));
}
break;
default:
System.out.println("Wrong choice");
break;
}
}while (true);
}
}