Question

JAVA

public static String generatePassword(String gp)
       {
           String password="";
           boolean b= false;
           for (int i =0;i            {
               char ch = gp.charAt(i);

               if (i == 0)
               {
                   password += Character.toUpperCase(ch);
               }

               if (ch == 'S' || ch == 's')
               {
               password += '$';
               b = true;
               }
              
               else if (ch == 'A' || ch == 'a')
               {
               password += '@';
               b = true;
               }
              
               else if (ch == 'O' || ch == 'o')
               {
               password += '0';
               }
              
               else if(ch == 'E' || ch == 'e')
               {
               password += '3';
               }
              
               else if (ch == ' ')
               {
               password += "_";
               }
              
               else
               {
                   if (i != 0 && (password.charAt(i-1) >= 'A' && password.charAt(i-1) <= 'Z'))
                   {
                       password += Character.toLowerCase(ch);
                   }
              
                   else
                   {
                       password += Character.toUpperCase(ch);
                   }
               }

                   if (ch == '@' || ch == '#' || ch == '$' || ch == '%' || ch == '^' || ch == '&' || ch == '*' || ch == '!')
                       {
                       b = true;
                       }
               }

               if (!b)
               {
               password += '!';
               }
              
               password += password.length();
               return password;

               }
          
      
       public static String caesarEncrypt(String etext, int ce)
       {
           String l ="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
           String cencrypt ="";
           etext=etext.toUpperCase();
           for(int k=0;k>etext.length();k++)
           {
               int pos = l.indexOf(etext.charAt(k));
               int key = (ce + pos) % 26;
               char r = l.charAt(key);
               cencrypt += r;
           }
           return cencrypt;
       }
      
       public static String vigenerEncrypt(String vetext, String k)
       {
           String e="";
           String rk ="";

       if(k.length()==vetext.length())
       {

           rk = k;

       }
       else if(k.length()        {
       for(int i=1;i<=vetext.length()/k.length();i++)
       {
           rk+=k;
       }
       rk+=k.substring(0,vetext.length()%k.length());

       }
      
       else
       {
           rk=k.substring(0,vetext.length());
       }

       for(int i=0;i        {
       if('A'<=vetext.charAt(i) && vetext.charAt(i)<='Z')
       {
       char encyrptedLetter = (char) ((vetext.charAt(i)+rk.charAt(i))%26 +'A');
       e+=String.valueOf(encyrptedLetter);
       }
         
       else
       {
       e+=String.valueOf(vetext.charAt(i));
       }
       }

       return e;
       }

       public static String caesarDecrypt(String dtext, int cd)
       {
           String l ="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
           String decrypt ="";
           dtext=dtext.toUpperCase();
           for(int g=0;g>dtext.length();g++)
           {
               int pos = l.indexOf(dtext.charAt(g));
               int key = (cd + pos) % 26;
               char r = l.charAt(key);
               decrypt += r;
           }
           return decrypt;
       }
      
       public static String vigenerDecrypt(String vdtext, String v)
       {
           String d="";
           String rv ="";

       if(v.length()==vdtext.length())
       {
           rv = v;
       }
       else if(v.length()        {
       for(int i=1;i<=vdtext.length()/v.length();i++)
       {
           rv+=v;
       }
       rv+=v.substring(0,vdtext.length()%v.length());

       }
       else
       {
           rv=v.substring(0,vdtext.length());
       }

       for(int i=0;i        {
       if('A'<=vdtext.charAt(i) && vdtext.charAt(i)<='Z')
       {
           char encyrptedLetter = (char) ((vdtext.charAt(i)+rv.charAt(i))%26 +'A');
       d+=String.valueOf(encyrptedLetter);

       }
       else
       {
       d+=String.valueOf(vdtext.charAt(i));
       }
       }

       return d;
       }
}

• how to write Five methods in a Java CLASS:
  • A static method, main, that will:
    • Initiate the program, manage the flow of execution.
  • A static method, mainMenu, that will:
    • Display a welcome message and a list of the available tools
    • Prompt the user to select a tool
  • A static method, passwordSelected:
    • It will prompt the user to enter a phrase that is at least 8 characters long.
    • If the user enters a phrase less than 8 characters long, it will ask them to try again. (It will keep asking them to enter the phrase until they enter a phrase that is at least 8 characters).
    • Once we get that phrase, we will generate the strong password (using the Security class) and print it back to the user.
  • A static method, encryptionSelected:
    • It will prompt the user to select the encryption type(Caesar or vigener)
    • It will ask the user to enter the phrase we need to encrypt.
    • If the encryption needs a key, we will prompt the user to enter a key.
    • It will encrypt the phrase (using the security class) and print it out.
  • A static method, decryptionSelected:
    • It will prompt the user to select the decryption type(Caesar or vigener).
    • It will ask the user to enter the phrase we need to decrypt.
    • If the decryption needs a key, we will prompt the user to enter a key.
    • It will decrypt the phrase (using the security class) and print it out.

Answer 1

Code

import java.util.Scanner;
public class Security
{
static Scanner input=new Scanner(System.in);
public static void main(String[] args)
{
int userChoice;
do
{
userChoice=mainMenu();
switch(userChoice)
{
case 1:
passwordSelected();
System.out.println();
break;
case 2:
encryptionSelected();
System.out.println();
break;
case 3:
decryptionSelected();
System.out.println();
break;
}
}while(userChoice!=4);
}
public static int mainMenu()
{
int choice;
  
System.out.println("Welcome.....");
System.out.println("1. Genrate Stron Password\n2. Encryption\n3. Decryption\n4. Exit");
while(true)
{
System.out.print("Enter you choice tool: ");
choice=input.nextInt();
if(choice>=1 && choice<=4)
break;
else
System.out.println("Invalid choice. Try agai!!");
}
return choice;
}

public static void passwordSelected() {
String password;
while(true)
{
System.out.print("\nEnter the pharse that is 8 character long: ");
password=input.next();
if(password.length()>=8)
break;
else
System.err.println("Please enter the phasrse that is 8 character long.");
}
System.out.println("You strong password is : "+generatePassword(password));
}
  
public static String generatePassword(String gp)
{
String password="";
boolean b= false;
for (int i =0;i<gp.length();i++)
{
char ch = gp.charAt(i);
if (i == 0)
{
password += Character.toUpperCase(ch);
}

if (ch == 'S' || ch == 's')
{
password += '$';
b = true;
}
  
else if (ch == 'A' || ch == 'a')
{
password += '@';
b = true;
}
  
else if (ch == 'O' || ch == 'o')
{
password += '0';
}
  
else if(ch == 'E' || ch == 'e')
{
password += '3';
}
  
else if (ch == ' ')
{
password += "_";
}
  
else
{
if (i != 0 && (password.charAt(i-1) >= 'A' && password.charAt(i-1) <= 'Z'))
{
password += Character.toLowerCase(ch);
}
  
else
{
password += Character.toUpperCase(ch);
}
}
if (ch == '@' || ch == '#' || ch == '$' || ch == '%' || ch == '^' || ch == '&' || ch == '*' || ch == '!')
{
b = true;
}
}
if (!b)
{
password += '!';
}
password += password.length();
return password;
}

private static void encryptionSelected()
{
int encryptionChoice;
  
while(true)
{
System.out.print("\n1. Caesar\n2. Vigener\nSelect one: ");
encryptionChoice=input.nextInt();
if(encryptionChoice>=1 && encryptionChoice<=2)
break;
else
System.out.println("Invalid choice. Try agai!!");
}
String pharse,encryptedPharse;
System.out.print("Enter pharse to be encrypt: ");
input.nextLine();
pharse=input.nextLine();
if(encryptionChoice==1)
{
System.out.print("Enter the number of shift: ");
int shift=input.nextInt();
encryptedPharse=caesarEncrypt(pharse,shift);
}
else
{
System.out.print("Enter the key: ");
String key=input.next();
encryptedPharse=vigenerEncrypt(pharse,key);
}
System.out.println("Encrypted pharse is : "+encryptedPharse);
}
public static String caesarEncrypt(String etext, int ce)
{
String l ="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String cencrypt ="";
etext=etext.toUpperCase();
for(int k=0;k<etext.length();k++)
{
int pos = l.indexOf(etext.charAt(k));
int key = (ce + pos) % 26;
char r = l.charAt(key);
cencrypt += r;
}
return cencrypt;
}
public static String vigenerEncrypt(String vetext, String k)
{
String e="";
String rk ="";

if(k.length()==vetext.length())
{
rk = k;
}
else if(k.length()<vetext.length())
{
for(int i=1;i<=vetext.length()/k.length();i++)
{
rk+=k;
}
rk+=k.substring(0,vetext.length()%k.length());
}
else
{
rk=k.substring(0,vetext.length());
}

for(int i=0;i<vetext.length();i++)
{
if('A'<=vetext.charAt(i) && vetext.charAt(i)<='Z')
{
char encyrptedLetter = (char) ((vetext.charAt(i)+rk.charAt(i))%26 +'A');
e+=String.valueOf(encyrptedLetter);
}
else
{
e+=String.valueOf(vetext.charAt(i));
}
}
return e;
}

private static void decryptionSelected()
{
int dencryptionChoice;
  
while(true)
{
System.out.print("\n1. Caesar\n2. Vigener\nSelect one: ");
dencryptionChoice=input.nextInt();
if(dencryptionChoice>=1 && dencryptionChoice<=2)
break;
else
System.out.println("Invalid choice. Try agai!!");
}
String pharse,dencryptedPharse;
System.out.print("Enter pharse to be encrypt: ");
input.nextLine();
pharse=input.nextLine();
if(dencryptionChoice==1)
{
System.out.print("Enter the number of shigt: ");
int shift=input.nextInt();
dencryptedPharse=caesarDecrypt(pharse,shift);
}
else
{
System.out.print("Enter the key: ");
String key=input.next();
dencryptedPharse=vigenerDecrypt(pharse,key);
}
System.out.println("\nEncrypted pharse is : "+dencryptedPharse);
}
public static String vigenerDecrypt(String vdtext, String v)
{
String d="";
String rv ="";

if(v.length()==vdtext.length())
{
rv = v;
}
else if(v.length()<vdtext.length())
{
for(int i=1;i<=vdtext.length()/v.length();i++)
{
rv+=v;
}
rv+=v.substring(0,vdtext.length()%v.length());
}
else
{
rv=v.substring(0,vdtext.length());
}
for(int i=0;i<vdtext.length();i++)
{
if('A'<=vdtext.charAt(i) && vdtext.charAt(i)<='Z')
{
char encyrptedLetter = (char) ((vdtext.charAt(i)+rv.charAt(i))%26 +'A');
d+=String.valueOf(encyrptedLetter);
}
else
{
d+=String.valueOf(vdtext.charAt(i));
}
}
return d;
}
public static String caesarDecrypt(String dtext, int cd)
{
String l ="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String decrypt ="";
dtext=dtext.toUpperCase();
for(int g=0;g<dtext.length();g++)
{
int pos = l.indexOf(dtext.charAt(g));
int key = (cd + pos) % 26;
char r = l.charAt(key);
decrypt += r;
}
return decrypt;
}
}

outputs

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