Caesar Cipher Encryption Decryption Java Source code

Written by Pranshu Bajpai | Join me on Google+ | LinkedIn

Source code for Caesar Cipher Encryption

package DICAss;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Pranshu
 */
public class DICAss12_CaesorCipherEnc {
    public static void main(String[] args)
    {
        String Msg = "IAMUNDERATTACKW";
        int Key = 3;
        
        String CTxt = "";
        
        int temp;
        char c;
        for(int i = 0 ; i < Msg.length() ; i++){
            if (Msg.charAt(i) + Key > 90){
                temp = (Msg.charAt(i) + Key) -26;
            }
            else{
                temp = (Msg.charAt(i) + Key); 
            }
            
            c = (char) temp;
            CTxt = CTxt + c;
        }        
        
        System.out.println(CTxt);
    }
}

Source Code for Caesar Cipher Decryption

package DICAss;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Pranshu
 */
public class DICAss13_CaesorCipherDec {
    public static void main(String[] args)
    {
        String CTxt = "LDPXQGHUDWWDFNZC";
        int Key = 3;
        
        String Msg = "";
        
        int temp, num;
        char c;
        for(int i = 0 ; i < CTxt.length() ; i++){
            num = ((CTxt.charAt(i) - Key) - 64);
            if ( num <= 0){
                temp = (90 - (num * (-1))%26);
            }
            else {
                temp = (( num % 26) + 64);
            }
            
            c = (char) temp;
            Msg = Msg + c;
        }              
        System.out.println(Msg);
    }
}

Cryptography with Java : Program Source Codes

5. For, While and Do While Loops in Java :

import java.io.*;
import java.util.*;
/**
 *
 * @author pranshu
 */
public class Loops_pranshu {
    public static void main(String[] args) throws IOException
    {
        System.out.println("Hello, Welcome to Pranshu's loops...");
        System.out.println("\nHow many times do you want to loop??  ");
        Scanner scn = new Scanner(System.in);
        int times = scn.nextInt();
        System.out.println("You Entered " + times);
        for(int i = 1; i <= times ; i++)
            System.out.println("Inside For Loop, The no. is " + i );
        int i = 1;
        do
        {
            System.out.println("Inside Do-While Loop, The no. is " + i );
            i++;
        } while(i <= times);
        
        i = 1;
        while( i <= times)
        {
            System.out.println("Inside While Loop, The no. is " + i );
            i++;
        }
    }
    
    
}

6. Conversion From Decimal to Binary in Java, Source code:

/**
 *
 * @author root
 */
public class conversions_pranshu {
    public static void main(String[] args) throws IOException
    {
        System.out.println("Enter a Decimal : ");
       BufferedReader brobj = new BufferedReader (new InputStreamReader(System.in));
        String dec = brobj.readLine();
        int dec2 = Integer.parseInt(dec);
        String bin = Integer.toBinaryString(dec2);
        System.out.println("The Binary is : " + bin);
    }
   
} 

7. Search for a Word in Text or String, Java Source code :

    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.util.regex.Matcher;
    import java.util.regex.Pattern;
/**
 *
 * @author pranshu
 */
public class matchtext {
    
   
    
    public static void main(String[] args)
    {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    System.out.println("Enter Text: ");
    try
    {
    String text = br.readLine();
    System.out.println("Enter the word to match : ");
    String word = br.readLine();
    String[] strarr = text.split(" ");
    int flag =0;
    for(String str:strarr)
    {
    if(str.equalsIgnoreCase(word))
    {
        System.out.println(word + " exists in " + text);    
        flag = 1;
    }
    }
    if(flag == 0)
        System.out.println("No match found");
    
    }
    catch(IOException e)
    {
    e.printStackTrace();
    }
    }
    } 

8. File Handling Program in Java : Write to a File: 

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

/**
 *
 * @author pranshu
 */
public class filehandle_pranshu {
    
    public static void main(String[] args) throws IOException
    {
          String com = "comment";
          String name = "uname";
 
          String ipadd = "127.0.0.1" ;

          FileWriter fstream = new FileWriter("/root/comments.txt",true);
          BufferedWriter fbw = new BufferedWriter(fstream);
            
            fbw.write(name + "__" + ipadd + ": ");
            fbw.write(com);
            fbw.newLine();
            System.out.println("Done Writing...");
            System.out.println("Closing File now...");
            fbw.close();
        
    }
    
}

Java Basic Programs With Source Code and Comments

Before starting with Cryptography in Java, these are some of the basic programs that I built quickly to brush up. 

1. Hello Java Source Code : 

            public static void main(String[] args) {

                System.out.println("Hello Java ! ~ ! ~");

        }

       

    }

2. Simple Input/Output Program Source Code :

    import java.io.IOException;

    import java.io.InputStreamReader; 

    public class InputOutput_pranshu {

        public static void main(String[] args) throws IOException

        {

            System.out.println("Hello, What's your name??  ");

            BufferedReader BRobj = new BufferedReader(new InputStreamReader(System.in) );

            String name = BRobj.readLine();

            System.out.println("Hello " + name + ", have a nice day");

        }

       

    }

3.  If Else Decision Making Java Source code :

 /**
 *
 * @author pranshu
 */
 public class IfElse_pranshu {
    public static void main(String[] args) throws IOException
    {
        System.out.println("Hello, Please Enter your name : ");
        BufferedReader brobj = new BufferedReader(new InputStreamReader(System.in)); 
        String name = brobj.readLine();
        if("pranshu".equals(name))
        {
         System.out.println("Hello Pranshu, Please Enter your Password : ");
         String pass = brobj.readLine();
            if("java".equals(pass))
                System.out.println("Welcome Pranshu, Access Granted!!");
            else
                System.out.println("Access Denied, Wrong Password");
        }
         else
            System.out.println("Sorry, this User is NOT Allowed Access");
           
    }
            
}

4. Convert A Char to its ASCII value, Java Source Code :

/**
 *
 * @author root
 */
public class Ascii_pranshu {
    public static void main(String[] args) throws IOException
    {
        System.out.println("Enter the Char you want to convert to ASCII :");
        BufferedReader BRobj = new BufferedReader(new InputStreamReader(System.in));
        String text = BRobj.readLine();
        int c = text.charAt(0);
        System.out.println("The ASCII Code is " + c);
    }
    }