eu.stratosphere.util.SimpleStringUtils Maven / Gradle / Ivy
/***********************************************************************************************************************
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
**********************************************************************************************************************/
package eu.stratosphere.util;
import java.io.Serializable;
import eu.stratosphere.types.StringValue;
/**
* Utility class for efficient string operations on strings. All methods in this class are
* written to be optimized for efficiency and work only on strings whose characters are
* representable in a single char, ie. strings without surrogate characters.
*/
public final class SimpleStringUtils {
/**
* Converts the given StringValue into a lower case variant.
*
* @param string The string to convert to lower case.
*/
public static void toLowerCase(StringValue string) {
final char[] chars = string.getCharArray();
final int len = string.length();
for (int i = 0; i < len; i++) {
chars[i] = Character.toLowerCase(chars[i]);
}
}
/**
* Replaces all non-word characters in a string by a given character. The only
* characters not replaced are the characters that qualify as word characters
* or digit characters with respect to {@link Character#isLetter(char)} or
* {@link Character#isDigit(char)}, as well as the underscore character.
*
* This operation is intended to simplify strings for counting distinct words.
*
* @param string The string value to have the non-word characters replaced.
* @param replacement The character to use as the replacement.
*/
public static void replaceNonWordChars(StringValue string, char replacement) {
final char[] chars = string.getCharArray();
final int len = string.length();
for (int i = 0; i < len; i++) {
final char c = chars[i];
if (!(Character.isLetter(c) || Character.isDigit(c) || c == '_')) {
chars[i] = replacement;
}
}
}
// ============================================================================================
/**
* A tokenizer for string values that uses whitespace characters as token delimiters.
* The tokenizer is designed to have a resettable state and operate on mutable objects,
* sparing object allocation and garbage collection overhead.
*/
public static final class WhitespaceTokenizer implements Serializable {
private static final long serialVersionUID = 1L;
private StringValue toTokenize; // the string to tokenize
private int pos; // the current position in the string
private int limit; // the limit in the string's character data
/**
* Creates a new tokenizer with an undefined internal state.
*/
public WhitespaceTokenizer() {}
/**
* Sets the string to be tokenized and resets the state of the tokenizer.
*
* @param string The string value to be tokenized.
*/
public void setStringToTokenize(StringValue string) {
this.toTokenize = string;
this.pos = 0;
this.limit = string.length();
}
/**
* Gets the next token from the string. If another token is available, the token is stored
* in the given target StringValue object.
*
* @param target The StringValue object to store the next token in.
* @return True, if there was another token, false if not.
*/
public boolean next(StringValue target) {
final char[] data = this.toTokenize.getCharArray();
final int limit = this.limit;
int pos = this.pos;
// skip the delimiter
for (; pos < limit && Character.isWhitespace(data[pos]); pos++);
if (pos >= limit) {
this.pos = pos;
return false;
}
final int start = pos;
for (; pos < limit && !Character.isWhitespace(data[pos]); pos++);
this.pos = pos;
target.setValue(this.toTokenize, start, pos - start);
return true;
}
}
// ============================================================================================
/**
* Private constructor to prevent instantiation, as this is a utility method encapsulating class.
*/
private SimpleStringUtils() {}
}