Class Alphabet

java.lang.Object

Alphabet

public class Alphabet
extends java.lang.Object

This is a library of methods to handle different alphabets. Every alphabet is a set of (16-bit) characters.

Aditional documentation: see Section 5.1, p.698, of "Algorithms, 4th Edition", by Robert Sedgewick e Kevin Wayne.

Field Summary

Fields

Modifier and Type	Field and Description
static Alphabet	ASCII This is the 128-character ASCII alphabet.
static Alphabet	BASE64 This is the 64-letter alphabet {A,B,..,Z,a,b,..,z,0,1,..,9,+,/}.
static Alphabet	BINARY This is the alphabet {0,1}.
static Alphabet	DECIMAL This is the alphabet {0,1,..,9}.
static Alphabet	DNA This is the alphabet {A,C,T,G}.
static Alphabet	EXTENDED_ASCII This is the 256-character extended ASCII alphabet.
static Alphabet	HEXADECIMAL This is the alphabet {0,1,..,9,A,..,F}.
static Alphabet	LOWERCASE This is the 26-letter alphabet {a,b,..,x,y,z}.
static Alphabet	OCTAL This is the alphabet {0,1,..,7}.
static Alphabet	PROTEIN This is the 20-letter alphabet {A,C,D,E,F,G,H,I,K,L,M,N,P,Q,R,S,T,V,W,Y}.
static Alphabet	UNICODE16 This is the 65536-character UNICODE alphabet.
static Alphabet	UPPERCASE This is the 26-letter alphabet {A,B,..,X,Y,Z}.

Constructor Summary

Constructors

Constructor and Description
Alphabet() Constructor 2 (extended ASCII).
Alphabet(java.lang.String alpha) Constructor 1.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	contains(char c) Is character c in the alphabet?.
int	lgR() Returns number of bits necessary to represent the index of a character.
static void	main(java.lang.String[] args) Test client (ignores command-line arguments).
int	R() Returns radix R.
char	toChar(int index) Converts an index between 0 and R-1 into a char over this alphabet.
java.lang.String	toChars(int[] indices) Converts array indices[] that represents a base-R integer into a String over this alphabet.
int	toIndex(char c) Converts character c to a number in 0..R-1.
int[]	toIndices(java.lang.String s) Receives a string s over this alphabet and converts s into a base-R int array.

Methods inherited from class java.lang.Object

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

Field Detail

BINARY

public static final Alphabet BINARY

This is the alphabet {0,1}.

OCTAL

public static final Alphabet OCTAL

This is the alphabet {0,1,..,7}.

DECIMAL

public static final Alphabet DECIMAL

This is the alphabet {0,1,..,9}.

HEXADECIMAL

public static final Alphabet HEXADECIMAL

This is the alphabet {0,1,..,9,A,..,F}.

DNA

public static final Alphabet DNA

This is the alphabet {A,C,T,G}.

LOWERCASE

public static final Alphabet LOWERCASE

This is the 26-letter alphabet {a,b,..,x,y,z}.

UPPERCASE

public static final Alphabet UPPERCASE

This is the 26-letter alphabet {A,B,..,X,Y,Z}.

PROTEIN

public static final Alphabet PROTEIN

This is the 20-letter alphabet {A,C,D,E,F,G,H,I,K,L,M,N,P,Q,R,S,T,V,W,Y}.

BASE64

public static final Alphabet BASE64

This is the 64-letter alphabet {A,B,..,Z,a,b,..,z,0,1,..,9,+,/}.

ASCII

public static final Alphabet ASCII

This is the 128-character ASCII alphabet.

EXTENDED_ASCII

public static final Alphabet EXTENDED_ASCII

This is the 256-character extended ASCII alphabet.

UNICODE16

public static final Alphabet UNICODE16

This is the 65536-character UNICODE alphabet. (65536 = 2^16.)

Constructor Detail

Alphabet

public Alphabet(java.lang.String alpha)

Constructor 1. Creates a new Alphabet from chars in string alpha. (Each char has 16 bits, of course.) Note: private array inverse[] will use 65536 positions, even for a small alphabet like DNA!

Alphabet

public Alphabet()

Constructor 2 (extended ASCII). Creates a new Alphabet consisting of Unicode chars 0 to 255.

Method Detail

contains

public boolean contains(char c)

Is character c in the alphabet?. (Implementation detail: Code assumes that the length of the private array inverse is 65536. This may result in memory waste in case of the DNA alphabet, for example, contrary to what the book says on page 700.)

R

public int R()

Returns radix R. This is the number of characters in the alphabet.

lgR

public int lgR()

Returns number of bits necessary to represent the index of a character. (This is ceiling( log_2( R)). Assumes, of course, that R >= 1.)

toIndex

public int toIndex(char c)

Converts character c to a number in 0..R-1. Each number in 0..R-1 corresponds to a unique character of this alphabet.

toIndices

public int[] toIndices(java.lang.String s)

Receives a string s over this alphabet and converts s into a base-R int array. Result is an array x[0..N-1] such that x[i] is toIndex(s.charAt(i)). Of course N is s.length().

toChar

public char toChar(int index)

Converts an index between 0 and R-1 into a char over this alphabet.

toChars

public java.lang.String toChars(int[] indices)

Converts array indices[] that represents a base-R integer into a String over this alphabet.

main

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

Test client (ignores command-line arguments). Converts the string "NowIsTheTimeForAllGoodMen" (over a BASE64 alphabet) to indices, then back to characters, and prints the result. Does the same for the string "AACGAACGGTTTACCCCG" (over the DNA alphabet). Does the same for the string "01234567890123456789" (over the DECIMAL alphabet).