Beginner Java Concepts

Switch Statement Algorithm

// Helper method to get an int value from a char.
public static int fromChar(char letter) {
	
	int returnInt = 0;
	
	switch(letter) {
		case 'a':
			returnInt = 1;
			break;
		case 'b':
			returnInt = 2;
			break;
		case 'c':
			returnInt = 3;
			break;
		case 'd':
			returnInt = 4;
			break;
		case 'e':
			returnInt = 5;
			break;
		case 'f':
			returnInt = 6;
			break;
		case 'g':
			returnInt = 7;
			break;
		case 'h':
			returnInt = 8;
			break;
		case 'i':
			returnInt = 9;
			break;
		case 'j':
			returnInt = 10;
			break;
		case 'k':
			returnInt = 11;
			break;
		case 'l':
			returnInt = 12;
			break;
		case 'm':
			returnInt = 13;
			break;
		case 'n':
			returnInt = 14;
			break;
		case 'o':
			returnInt = 15;
			break;
		case 'p':
			returnInt = 16;
			break;
		case 'q':
			returnInt = 17;
			break;
		case 'r':
			returnInt = 18;
			break;
		case 's':
			returnInt = 19;
			break;
		case 't':
			returnInt = 20;
			break;
		case 'u':
			returnInt = 21;
			break;
		case 'v':
			returnInt = 22;
			break;
		case 'w':
			returnInt = 23;
			break;
		case 'x':
			returnInt = 24;
			break;
		case 'y':
			returnInt = 25;
			break;
		case 'z':
			returnInt = 26;
			break;
		default:
			returnInt = -1000;
	}
	
	return returnInt;
}

// Helper method to get a char from an int value.
public static char fromInt(int value) {
	
	char returnChar = ' ';
	
	switch(value) {
		case 1:
			returnChar = 'a';
			break;
		case 2:
			returnChar = 'b';
			break;
		case 3:
			returnChar = 'c';
			break;
		case 4:
			returnChar = 'd';
			break;
		case 5:
			returnChar = 'e';
			break;
		case 6:
			returnChar = 'f';
			break;
		case 7:
			returnChar = 'g';
			break;
		case 8:
			returnChar = 'h';
			break;
		case 9:
			returnChar = 'i';
			break;
		case 10:
			returnChar = 'j';
			break;
		case 11:
			returnChar = 'k';
			break;
		case 12:
			returnChar = 'l';
			break;
		case 13:
			returnChar = 'm';
			break;
		case 14:
			returnChar = 'n';
			break;
		case 15:
			returnChar = 'o';
			break;
		case 16:
			returnChar = 'p';
			break;
		case 17:
			returnChar = 'q';
			break;
		case 18:
			returnChar = 'r';
			break;
		case 19:
			returnChar = 's';
			break;
		case 20:
			returnChar = 't';
			break;
		case 21:
			returnChar = 'u';
			break;
		case 22:
			returnChar = 'v';
			break;
		case 23:
			returnChar = 'w';
			break;
		case 24:
			returnChar = 'x';
			break;
		case 25:
			returnChar = 'y';
			break;
		case 26:
			returnChar = 'z';
			break;
		default:
			returnChar = '@';
	}
	
	return returnChar;
}

// Actual ROT13 encryption method.
public static String encrypt(String plainText) {
	
	// Declare variables to be used in the encryption process.
	String cipherText = "";
	char newChar = ' ';
	int charVal = 0;
	char currentChar = ' ';
	boolean isUpperCase = false;
	
	// Loop through each char in plainText and calculate the encrypted char.
	for(int i = 0; i < plainText.length();i++) {
		currentChar = plainText.charAt(i);
		
		// Check to see if the char is capitalized. 
		// Set the boolean variable to true if it is.
		if(Character.isUpperCase(currentChar)) {
			isUpperCase = true;
			currentChar = Character.toLowerCase(currentChar);
		}
		
		// Calculate the int value for the new char.
		charVal = fromChar(currentChar) + 13;
		//System.out.println(currentChar);
		//System.out.println("charVal: " + charVal);
		
		// If the new value is higher than 26, or higher than our alphabet,
		// adjust it to be circular.
		// By circular, I mean wrap the sequence around and start back at 
		// the beginning.
		if(charVal > 26) {
			charVal = charVal - 26;
		}

		//System.out.println("charVal is now: " + charVal);

		
		// Calculate the corresponding char from the int value. 
		// If char is non alpha, no change is needed.
		if(charVal < 0) {
			newChar = currentChar;
		} else {
			newChar = fromInt(charVal);
		}
		
		// If the plain text char was upper case, make the cipher 
		// text char upper case as well.
		if(isUpperCase) {
			cipherText += Character.toUpperCase(newChar);
		} else {
			cipherText += newChar;
		}
		isUpperCase = false;
	}
	
	// Return the cipherText produced from the plainText.
	return cipherText;
}

public static void main(String[] args) {
	String test = encrypt("This is A NEW test, let's see how this works. Low and HiGh abcdefghijklmnopqrstuvwxyz!?()");
	System.out.println(test);
	String test2 = encrypt("Guvf vf N ARJ grfg, yrg'f frr ubj guvf jbexf. Ybj naq UvTu nopqrstuvwxyzabcdefghijkym!?()");
	System.out.println(test2);
}