PolybiusSquareCipher.java

import java.util.Scanner;

public class PolybiusSquareCipher{
	
	static char[][] table = new char[5][5];
	
	static void createTable()
	{
		for(int i=0;i<2;i++)
			for(int j=0;j<5;j++) {
				if(i*5+j+65!=74)
					table[i][j]=(char)(i*5+j+65);
			}
		table[1][4]='K';
		for(int i=2;i<5;i++)
			for(int j=0;j<5;j++)
				table[i][j]=(char)(i*5+j+65+1);
	}

	static String encrypt(String pt) {
		String encpt = "";
		char[] encpt1 = pt.toCharArray();
		for(int i=0; i<pt.length(); i++) {
			for(int j=0; j<5; j++)
				for(int k=0; k<5; k++) {
					if(encpt1[i]=='J') {
						encpt=encpt+"24";
						break;
					}
					if(table[j][k]==encpt1[i]) {
						encpt=encpt+Integer.toString(j+1)+Integer.toString(k+1);
						break;
					}
				}
		}
		return encpt;
	}

	static String decrypt(String encpt) {
		String decpt="";
		char[] decpt1 = encpt.toCharArray();
		for(int i=0; i<encpt.length(); i=i+2) {
			int row = Integer.parseInt(String.valueOf(decpt1[i]));
			int col = Integer.parseInt(String.valueOf(decpt1[i+1]));
			decpt=decpt+Character.toString(table[row-1][col-1]);
		}
		return decpt;
	}
	
	public static void main(String[] args) {
		
		String pt,encpt,decpt;
		System.out.print("Enter plaintext: ");
		Scanner scanner = new Scanner(System.in);
		pt = scanner.nextLine();
		createTable();
		encpt = encrypt(pt);
		System.out.println("Encrypted text: "+encpt);
		decpt = decrypt(encpt);
		System.out.println("Decrypted text: "+decpt);

	}
	
}