net.sf.mmm.util.text.base

Class FastStringHasher

java.lang.Object

net.sf.mmm.util.text.base.AbstractStringHasher

net.sf.mmm.util.text.base.FastStringHasher

All Implemented Interfaces:

StringHasher

public class FastStringHasher
extends AbstractStringHasher

This is a fast implementation of StringHasher.

Since:

2.0.0

Author:

Joerg Hohwiller (hohwille at users.sourceforge.net)

Field Summary

Fields

Modifier and Type	Field and Description
private static int	HASH_FACTOR The hash-factor - should be prime (however Bernstein uses 33).

Constructor Summary

Constructors

Constructor and Description
FastStringHasher() The constructor.

Method Summary

Modifier and Type	Method and Description
int	getHashCode(char[] string, int start, int end) This method gets the hash-code for the specified subsequence of the given string.
int	getHashCode(CharSequence string, int start, int end) This method gets the hash-code for the specified subsequence of the given string.
int[]	getHashCodes(char[] string, int length, int stringStart, int stringEnd) This method gets the hash-codes for all subsequence of string from stringStart (inclusive) until stringEnd (exclusive) that have the given length.

Methods inherited from class net.sf.mmm.util.text.base.AbstractStringHasher

getHashCode, getHashCodes, getHashCodes, getHashCodes

Methods inherited from class java.lang.Object

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

Field Detail

HASH_FACTOR

private static final int HASH_FACTOR

The hash-factor - should be prime (however Bernstein uses 33).

See Also:

Constant Field Values

Constructor Detail

FastStringHasher

public FastStringHasher()

The constructor.

Method Detail

getHashCode

public int getHashCode(char[] string,
                       int start,
                       int end)

Description copied from interface: StringHasher

This method gets the hash-code for the specified subsequence of the given string.

Parameters:

string - is the char-array containing the substring to hash.

start - is the index of the first character to include into the hash.

end - is the index one before the last character to include into the hash.

Returns:

the according hash-code.

See Also:

Object.hashCode()

getHashCode

public int getHashCode(CharSequence string,
                       int start,
                       int end)

Description copied from interface: StringHasher

This method gets the hash-code for the specified subsequence of the given string.

Specified by:

getHashCode in interface StringHasher

Overrides:

getHashCode in class AbstractStringHasher

Parameters:

string - is the CharSequence containing the subsequence to hash.

start - is the index of the first character to include into the hash.

end - is the index one before the last character to include into the hash.

Returns:

the according hash-code.

See Also:

Object.hashCode()

getHashCodes

public int[] getHashCodes(char[] string,
                          int length,
                          int stringStart,
                          int stringEnd)

Description copied from interface: StringHasher

This method gets the hash-codes for all subsequence of string from stringStart (inclusive) until stringEnd (exclusive) that have the given length.
The implementation of this method needs to behave functionally equivalent to this code (but should be more efficient):

 int size = stringEnd - stringStart - length + 1;
 if (size <= 0) {
   return new int[0];
 }
 int[] result = new int[size];
 for (int i = 0; i < size; i++) {
   result[i] = getHashCode(string, i, i + length);
 }
 return result;
 

Specified by:

getHashCodes in interface StringHasher

Overrides:

getHashCodes in class AbstractStringHasher

Parameters:

string - is the string as char-array.

length - is the length of the sub-sequences of string to hash.

stringStart - is the index where to start in string.

stringEnd - is the index where to stop in string.

Returns:

the requested hash-codes. An empty array if the length of string is less than the given length.