Class CaesarCipher

java.lang.Object

CaesarCipher

public class CaesarCipher
extends java.lang.Object

A class that "encrypts" data through a simple transformation.

The provided code is incomplete. Modify it so that it works properly and passes the unit tests in CaesarCipherTest.java.

See Also:

MP3 Documentation, Caesar Cipher Documentation

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_SHIFT Maximum shift that encrypt and decrypt need to handle.
static int	MIN_SHIFT Minimum shift that encrypt and decrypt need to handle.
static int	TRANSFORM_MODULUS Modulo to use for our transformation.

Constructor Summary

Constructors

Constructor and Description
CaesarCipher()

Method Summary

Modifier and Type	Method and Description
static char[]	decrypt(char[] line, int shift) Decrypt a single line of text using a rotate-N transformation.
static char[]	encrypt(char[] line, int shift) Encrypt a single line of text using a rotate-N transformation.
static void	main(java.lang.String[] unused) Solicits a single line of text from the user, encrypts it using a random shift, and then decrypts it.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MIN_SHIFT

public static final int MIN_SHIFT

Minimum shift that encrypt and decrypt need to handle.

See Also:

Constant Field Values

MAX_SHIFT

public static final int MAX_SHIFT

Maximum shift that encrypt and decrypt need to handle.

See Also:

Constant Field Values

TRANSFORM_MODULUS

public static final int TRANSFORM_MODULUS

Modulo to use for our transformation.

See Also:

Constant Field Values

Constructor Detail

CaesarCipher

public CaesarCipher()

Method Detail

encrypt

public static char[] encrypt(char[] line,
                             int shift)

Encrypt a single line of text using a rotate-N transformation.

The printable range of ASCII characters starts at decimal value 32 (' ') and ends at 126 ('~'). You should shift characters within this range by the shift value provided. For example, ' ' (32) shift 1 becomes '!' (33), while '~' (126) shift 1 wraps around and becomes ' ' (32). You may want to explore modular arithmetic to simplify the transformation.

Your function should return a new character array, not modify the one that it is passed.

Both encrypt and decrypt may receive invalid inputs. If the character array contains invalid characters (outside of the range defined above), or if the shift value is outside the range defined above (e.g., larger than MAX_SHIFT), you should return null.

Your solution must match the expected output exactly, otherwise you will not receive credit.

Complete the Javadoc comment for this function and write it.

Parameters:

line - array of characters to encrypt

shift - amount to shift each character

Returns:

line encryped by rotating the specified amount

See Also:

ASCII Character Table

decrypt

public static char[] decrypt(char[] line,
                             int shift)

Decrypt a single line of text using a rotate-N transformation.

See comment for encrypt above.

Parameters:

line - array of characters to decrypt

shift - amount to shift each character

Returns:

line decrypted by rotating the specified amount

See Also:

ASCII Character Table

main

public static void main(java.lang.String[] unused)

Solicits a single line of text from the user, encrypts it using a random shift, and then decrypts it.

You are free to review this function, but should not modify it. Note that this function is not tested by the test suite, as it is purely to aid your own interactive testing.

Parameters:

unused - unused input arguments