Creating ciphers and adding Caesar Cipher

Author: ffahri

ciphers/Caesar.java

@@ -0,0 +1,117 @@
+/**
+Author : FAHRI YARDIMCI
+
+A Java implementation of Caesar Cipher.
+/It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. /
+**/
+import java.util.Scanner;
+public class Caesar {
+public static String encode (String message,int shift)
+{
+	String encoded = "";
+	for(int i = 0 ; i<message.length() ;i++)
+	{
+		int current = message.charAt(i); //using char to shift characters because ascii is in-order latin alphabet
+		if(current==32)
+		{
+			encoded += " ";
+			continue;
+
+		}
+		else if (current>=65 && current<= 90)
+		{
+			int numAlphabet = message.charAt(i);
+			if(shift + numAlphabet > 90)
+			{
+				int j = 90 - numAlphabet;
+				char nextKey = (char)(65 + (shift - j - 1));
+				encoded += nextKey;
+				
+			}
+			else
+			{
+				char nextKey = (char)(current + shift);
+				encoded += nextKey;
+			}
+		}
+		else if (current>=97 && current <= 122)
+		{
+			int numAlphabet = message.charAt(i);
+			if(shift + numAlphabet > 122)
+			{
+				int j = 122 - numAlphabet;
+				char nextKey = (char)(97 + (shift - j - 1));
+				encoded += nextKey;
+			}
+			else
+			{
+				char nextKey = (char)(current + shift);
+				encoded += nextKey;
+			}
+		}
+	}
+	return encoded;
+}
+public static String decode (String message,int shift)
+{
+	String decoded = "";
+	for(int i = 0 ; i<message.length() ;i++)
+	{
+		int current = message.charAt(i);
+		if(current==32)
+		{
+			decoded += " ";
+			continue;
+
+		}
+		else if (current>=65 && current<= 90)
+		{
+			int numAlphabet = message.charAt(i);
+			if(numAlphabet - shift < 65)
+			{
+				int j = numAlphabet - 65;
+				char nextKey = (char)(90 - (shift - j - 1));
+				decoded += nextKey;
+				
+			}
+			else
+			{
+				char nextKey = (char)(current - shift);
+				decoded += nextKey;
+			}
+		}
+		else if (current>=97 && current <= 122)
+		{
+			int numAlphabet = message.charAt(i);
+			if(numAlphabet - shift < 97)
+			{
+				int j = numAlphabet - 97;
+				char nextKey = (char)(122 - (shift - j - 1));
+				decoded += nextKey;
+			}
+			else
+			{
+				char nextKey = (char)(current - shift);
+				decoded += nextKey;
+			}
+		}
+	}
+	return decoded;
+}
+public static void main(String[] args)
+{
+	Scanner input = new Scanner(System.in);
+	System.out.println("Please enter the message (Latin Alphabet)");
+	String message = input.nextLine();
+	System.out.println(message);
+	System.out.println("Please enter the shift number");
+	int shift = input.nextInt() % 26;
+	System.out.println("(E)ncode or (D)ecode ?");
+	char choice = input.next().charAt(0);
+	if(choice == 'E' || choice=='e')
+		System.out.println("ENCODED MESSAGE IS \n" + encode(message,shift)); //send our function to handle
+	if(choice =='D' || choice =='d')
+		System.out.println("DECODED MESSAGE IS \n" + decode(message,shift));
+}
+
+}