Very Simple Encryption

[AndrewM16921]

Hi, my friend asked me to make him a very simple program that could generate an encryption substitution code, enter your own code, and encrypt and decrypt a text file. So, i started to make the programs... and eventually I got them all to work. But I had a few problems, and I wanted to know if there were any easier or more efficient ways for me to do some things I did. This is a low priority request, as the programs do work just fine. I just wish to better my habits if anything I did is a bad practice. Anyway, any advice is appreciated. Thanks. :)

CryptGen - Generates a random substitution code and saves to a file.

import java.util.Random;
import java.io.*;

public class CryptGen
{
	public static void main(String[] args)throws IOException
	{
		Random gen = new Random();
		PrintWriter write = new PrintWriter(new File("CryptCode.txt"));
		char[] chars = new char[] {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
									'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
		char[] cryptList = new char[52];

		int tracker = 0;
		while(tracker < 52)
		{
			int num = gen.nextInt(52);
			if(cryptList[num] == '\u0000')
			{
			cryptList[num] = chars[tracker];
			tracker++;
			}
		}
		
		for(int i = 0; i < 52; i++)
		{
			write.println(chars[i] + " " + cryptList[i]);
		}
		write.close();
	}
}

CryptMaker - Allows you to enter a substitution code and saves it to a file.

import java.util.Scanner;
import java.io.*;

public class CryptMaker
{
	public static void main(String[] args)throws IOException
	{
		Scanner read = new Scanner(System.in);
		PrintWriter write = new PrintWriter(new File("CryptCode.txt"));
		char[] chars = new char[] {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
									'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
		char[] cryptList = new char[52];

		for(int i = 0; i < 52; i++)
		{
			System.out.print(chars[i] + ": ");
			cryptList[i] = read.nextLine().charAt(0);
		}
		
		for(int i = 0; i < 52; i++)
		{
			write.println(chars[i] + " " + cryptList[i]);
		}
		write.close();
	}
}

Encrypt - Encrypts the plain text.

import java.util.*;
import java.io.*;

public class Encrypt
{
	public static void main(String[] args)throws IOException
	{
		Scanner read = new Scanner(new File("PlainText.txt"));
		PrintWriter write = new PrintWriter(new File("CipherText.txt"));
		String word;
		char chars[];
		
		while(read.hasNext())
		{
			word = read.next();
			int length = word.length();
			chars = new char[length];
			for(int i = 0; i < length; i++)
			{
				chars[i] = word.charAt(i);
			}
			chars = Substitution(chars, length);
			chars = Transposition(chars, length);

			word = "";
			for(int i = 0; i < length; i++)
			{
				word = word + chars[i];
			}
			write.print(word + " ");
			//System.out.print(word + " ");
		}	
		write.close();
	}
	
	public static char[] Transposition(char[] chars, int length)
	{
		char transposed[] = new char[length];
		for(int i = 0; i < length && i+2 <= length; i+=2)
		{
			transposed[i] = chars[i+1];
			transposed[i+1] = chars[i];
		}
		return transposed;
	}
	
	public static char[] Substitution(char[] chars, int length)throws IOException
	{
		Scanner getCode = new Scanner(new File("CryptCode.txt"));
		char plainChars[] = new char[52];
		char cipherChars[] = new char[52];
		for(int i = 0; i < 52; i++)
		{
			String line = getCode.nextLine();
			plainChars[i] = line.charAt(0);
			cipherChars[i] = line.charAt(2);
		}
		
		for(int i = 0; i < length; i++)
		{
			for(int j = 0; j < 52; j++)
			{
				if(chars[i] == plainChars[j])
				{
					chars[i] = cipherChars[j];
					break;
				}
			}
		}

		return chars;
	}
}

Decrypt - Decrypts the cipher text.

import java.util.*;
import java.io.*;

public class Decrypt
{
	public static void main(String[] args)throws IOException
	{
		Scanner read = new Scanner(new File("CipherText.txt"));
		PrintWriter write = new PrintWriter(new File("PlainText.txt"));
		String word;
		char chars[];
		
		while(read.hasNext())
		{
			word = read.next();
			int length = word.length();
			chars = new char[length];
			for(int i = 0; i < length; i++)
			{
				chars[i] = word.charAt(i);
			}
			chars = Substitution(chars, length);
			chars = Transposition(chars, length);

			word = "";
			for(int i = 0; i < length; i++)
			{
				word = word + chars[i];
			}
			write.print(word + " ");
			//System.out.print(word + " ");
		}	
		write.close();
	}
	
	public static char[] Transposition(char[] chars, int length)
	{
		char transposed[] = new char[length];
		for(int i = 0; i < length && i+2 <= length; i+=2)
		{
			transposed[i] = chars[i+1];
			transposed[i+1] = chars[i];
		}
		return transposed;
	}
	
	public static char[] Substitution(char[] chars, int length)throws IOException
	{
		Scanner getCode = new Scanner(new File("CryptCode.txt"));
		char plainChars[] = new char[52];
		char cipherChars[] = new char[52];
		for(int i = 0; i < 52; i++)
		{
			String line = getCode.nextLine();
			plainChars[i] = line.charAt(0);
			cipherChars[i] = line.charAt(2);
		}
		
		for(int i = 0; i < length; i++)
		{
			for(int j = 0; j < 52; j++)
			{
				if(chars[i] == cipherChars[j])
				{
					chars[i] = plainChars[j];
					break;
				}
			}
		}

		return chars;
	}
}

[AndrewM16921]

Also, I tried to get an Expansion method to work. Unfortunately, I never got it to work quite right. I think it has something to do with my need to change the array size of chars[], so I'll figure it out eventually. If you have some hints for that, I could use them. Also, if anyone has some additional ideas for things I could add to this, let me know. Thanks. :)

[Poincare]

Just a suggestion, if you know C, it might just might just better to use that instead of java. Then again, I'm a n00b.

[AndrewM16921]

I wasn't expecting that from a Java forum, lol. But why would you suggest C for this, rather than Java?

[CJSLMAN]

Poincare... OK, I'll bite... why do you think this assignment would be better to do in C, than in Java?

CJSL

[Fubarable]

I wasn't expecting that from a Java forum, lol. But why would you suggest C for this, rather than Java?

Simple if the only tool you have is a hammer, pretty soon everything starts looking like a nail. Mr. Andrew, I suggest you ignore poncaire's "advice".