Implementation One time pad cipher in Java

// File Name: OneTimePad.java
import java.util.*;
class msg{
 int a=97;
 char all[]=new char[27];

 msg()
 {
  for(int i=0;i < 26;i++)
  { 
   all[i]=(char)a;
   a++; 
  }
 }

 int Ipos(char c)
 {
  int i=0;
  for(;i < 26;i++)
  {
   if(all[i]==c)
   {
    break;
   }
  }
  return i;
 }
 
 char Cpos(int c)
 {
  int i=0;
  for(;i < c;i++)
  {
   
  }
  return all[i];
 }
}
class OneTimePadCipherImplementation{
 String Encryption(String plaintext,String key)
 {
  plaintext=plaintext.toLowerCase();
  msg m1=new msg();
  int pt[]=new int[plaintext.length()];
  int k[]=new int[key.length()];
  int ct[]=new int[plaintext.length()];
  
  for(int i=0;i < plaintext.length();i++)
  {
   pt[i]=m1.Ipos(plaintext.charAt(i));
  }
  for(int i=0;i < key.length();i++)
  {
   k[i]=m1.Ipos(key.charAt(i));
  }
  int j=0;
  for(int i=0;i < plaintext.length();i++)
  {
   ct[i]=pt[i]+k[j];
   j++;
   if(j==key.length())
    j=0; 
   if(ct[i]>26)
    ct[i]=ct[i]%26;
  }
  String cipher="";
  for(int i=0;i < plaintext.length();i++)
  {
   cipher+=m1.Cpos(ct[i]);
  }
  
  return cipher;
 }
 
 
 
 String Decryption(String ciphertext,String key)
 {
  String plaintext="";
  msg m1=new msg();
  int pt[]=new int[ciphertext.length()];
  int k[]=new int[key.length()];
  int ct[]=new int[ciphertext.length()];
  
  for(int i=0;i < ciphertext.length();i++)
  {
   ct[i]=m1.Ipos(ciphertext.charAt(i));
  }
  for(int i=0;i < key.length();i++)
  {
   k[i]=m1.Ipos(key.charAt(i));
  }
  int j=0;
  for(int i=0;i < ciphertext.length();i++)
  {
   pt[i]=ct[i]-k[j];
   j++;
   if(j==key.length())
    j=0; 
   if(pt[i] < 0)
    pt[i]+=26;
  }
  String cipher="";
  for(int i=0;i < ciphertext.length();i++)
  {
   plaintext+=m1.Cpos(pt[i]);
  }
  return plaintext;
 }
}







class OneTimePad{
 public static void main(String args[])throws Exception
 {
  
  
  String plaintext,key;
  Scanner scn=new Scanner(System.in);
  
  
  System.out.println("Enter plaintext:");
  plaintext=scn.nextLine();
  System.out.println("Enter key:");
  key=scn.nextLine();

  OneTimePadCipherImplementation OneTimePad=new OneTimePadCipherImplementation();
  
  String ciphertext=OneTimePad.Encryption(plaintext,key);
  
  System.out.println("Encrpted text is:"+ciphertext);
  
  
  System.out.println("Decrypted text is:"+OneTimePad.Decryption(ciphertext,key));

 }
}

OUTPUT

Enter plaintext:
onetimepadalogrihtmsneedlongkey
Enter key:
longkeyisrequiredforonetimepad
Encrpted text is:zbrzsqcxsuebioimky jbriwt rvkhj
Decrypted text is:onetimepadalogrihtmsneedlongkey