Java implementation of Caesar Cipher algorithm

Caesar-Cipher/Java/irisyuan/caesarCipher.java

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+import java.util.Scanner;
+
+public class caesarCipher {
+
+	// cipher(String,int) returns original message shifted by 3 letters
+	// if input is numerical, adds 3 to number
+	public static char[] cipher(String message, int shift) {
+
+		// declare variables
+		String s = message;
+		// convert string to array of chars
+		char[] letters = message.toCharArray();
+
+		for(int i = 0; i < message.length(); i++){
+	       letters[i] += 3;
+		}
+		return letters;
+	}
+
+	// main method takes user input and calls cipher
+	public static void main(String[] args) {
+
+		Scanner input = new Scanner(System.in);
+		System.out.println("Plaintext: ");
+		String message = input.nextLine();
+
+		System.out.println("Ciphertext:");
+		System.out.println(cipher(message, 3));
+	}
+
+}