SubCipher.java

import java.io.Console;


public class SubCipher{

	private String keyPhrase,keyCipher;
	public String alphabet="";
	public SubCipher(String key){
		
		keyCipher="";
		keyPhrase=key;
		this.generateAlphabet();
		this.generateCipher();
	}

	public void generateAlphabet(){
		//used to generate string of alphabet a to z
		for(char c = 'a'; c <= 'z'; c++){
				
 			alphabet+=c;

		}	
		
	}
	private void generateCipher(){
		
			// remove spaces
			String [] phraseNoSpaces = keyPhrase.split(" ");
			
			for(int i=0;i<phraseNoSpaces.length;i++){
				keyCipher+=phraseNoSpaces[i];
					
			}
		
			
			//remove duplicate characters
			
			String [] cipherCharRemoved;
			
			for(int i=0;i<keyCipher.length();i++){
				
				String firstChar=keyCipher.substring(i,(i+1));
				
				
				String subString1= keyCipher.substring(0,(i+1));
				
				
				String subString2 = keyCipher.substring((i+1),keyCipher.length());
				
						
				cipherCharRemoved = subString2.split(firstChar); 
				
				keyCipher=subString1;
				
				for(int j=0;j<cipherCharRemoved.length;j++){
				
					keyCipher+=cipherCharRemoved[j];
					
				}
				
			}
			
		
			
			

			for(char c = 'z'; c >= 'a'; c--){ //loop through alphabet, adding characters which aren't in the cipherKey
				
				if(keyCipher.indexOf(c)==-1){ 
					
 					keyCipher+=c;
					
				}
 			   
			}
			
			
	}	
	
	public String encrypt(String plainText){ // encrypts plaintext with generated cipher
		
		String cipherText="";
		for(int i=0;i<plainText.length();i++){
			
			char currentChar=plainText.charAt(i);
			
			if(Character.isLetter(currentChar)){ 
				if(Character.isUpperCase(currentChar)){
				
					cipherText+=String.valueOf(Character.toUpperCase(keyCipher.charAt(alphabet.indexOf(Character.toLowerCase(currentChar)))));
			
				}
				
				else{
					cipherText+=String.valueOf(keyCipher.charAt(alphabet.indexOf(currentChar)));
				}
			}
			else{
			
				cipherText+=String.valueOf(currentChar);	
				
			}
			
		}
		return cipherText;
	}
	
	public String decrypt(String cipherText){ // decrypts ciphertext with generated cipher
		
		String plainText="";
		for(int i=0;i<cipherText.length();i++){
			
			char currentChar=cipherText.charAt(i);
			
			if(Character.isLetter(currentChar)){ 
			
				if(Character.isUpperCase(currentChar)){
				
					plainText+=String.valueOf((Character.toUpperCase(alphabet.charAt(keyCipher.indexOf(Character.toLowerCase(currentChar))))));
			
				}
				else{
				
					plainText+=String.valueOf(alphabet.charAt(keyCipher.indexOf(currentChar)));
			
				}
			}
			else{
				
				plainText+=String.valueOf(currentChar);	
					
			}
		}
		return plainText;
	}
	

		
	public static void main(String[]args){
	
		if(args.length>0){ 
			
			Console c = System.console(); //declare and assign console which will be used to get input from user
			String keyPhrase = c.readLine("input a key phrase: "); //prompt user to input key phrase
			SubCipher sb=new SubCipher(keyPhrase); //create subcipher with keyphrase provided by user
			
			if(args[0].equals("-e")){ // if user wishes to perform encryption
				
				String plainText = c.readLine("input plaintext: "); //prompt user to input plaintext to be encrypted
				System.out.println("Encrypted text: "+sb.encrypt(plainText)); //output ciphertext generated from plaintext
				
			}
			
			else if(args[0].equals("-d")){ if user wishes to perform decryption
				
				String cipherText = c.readLine("input ciphertext: "); //prompt user to input ciphertext to be decrypted
				System.out.println("Decrypted text: "+sb.decrypt(cipherText)); //output plaintext generated from ciphertext
				
			}
		}
	
	}


}