com.firefly.utils.lang.StringParser Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 com.firefly.utils.lang;
/**
* Utility class for string parsing that is higher performance than
* StringParser for simple delimited text cases. Parsing is performed
* by setting the string, and then using the findXxxx() and
* skipXxxx() families of methods to remember significant
* offsets. To retrieve the parsed substrings, call the extract()
* method with the appropriate saved offset values.
*
* @author Craig R. McClanahan
* @version $Id: StringParser.java 939353 2010-04-29 15:50:43Z kkolinko $
*/
public final class StringParser {
// ----------------------------------------------------------- Constructors
/**
* Construct a string parser with no preset string to be parsed.
*/
public StringParser() {
this(null);
}
/**
* Construct a string parser that is initialized to parse the specified
* string.
*
* @param string The string to be parsed
*/
public StringParser(String string) {
super();
setString(string);
}
// ----------------------------------------------------- Instance Variables
/**
* The characters of the current string, as a character array. Stored
* when the string is first specified to speed up access to characters
* being compared during parsing.
*/
private char chars[] = null;
/**
* The zero-relative index of the current point at which we are
* positioned within the string being parsed. NOTE:
* the value of this index can be one larger than the index of the last
* character of the string (i.e. equal to the string length) if you
* parse off the end of the string. This value is useful for extracting
* substrings that include the end of the string.
*/
private int index = 0;
/**
* The length of the String we are currently parsing. Stored when the
* string is first specified to avoid repeated recalculations.
*/
private int length = 0;
/**
* The String we are currently parsing.
*/
private String string = null;
// ------------------------------------------------------------- Properties
/**
* Return the zero-relative index of our current parsing position
* within the string being parsed.
*
* @return The current index
*/
public int getIndex() {
return (this.index);
}
/**
* Return the length of the string we are parsing.
* @return The length of this string
*/
public int getLength() {
return (this.length);
}
/**
* Return the String we are currently parsing.
* @return The current string
*/
public String getString() {
return (this.string);
}
/**
* Set the String we are currently parsing. The parser state is also reset
* to begin at the start of this string.
*
* @param string The string to be parsed.
*/
public void setString(String string) {
this.string = string;
if (string != null) {
this.length = string.length();
chars = this.string.toCharArray();
} else {
this.length = 0;
chars = new char[0];
}
reset();
}
// --------------------------------------------------------- Public Methods
/**
* Advance the current parsing position by one, if we are not already
* past the end of the string.
*/
public void advance() {
if (index < length)
index++;
}
/**
* Extract and return a substring that starts at the specified position,
* and extends to the end of the string being parsed. If this is not
* possible, a zero-length string is returned.
*
* @param start Starting index, zero relative, inclusive
* @return The result string from start
*/
public String extract(int start) {
if ((start < 0) || (start >= length))
return ("");
else
return (string.substring(start));
}
/**
* Extract and return a substring that starts at the specified position,
* and ends at the character before the specified position. If this is
* not possible, a zero-length string is returned.
*
* @param start Starting index, zero relative, inclusive
* @param end Ending index, zero relative, exclusive
* @return The result string from start to end
*/
public String extract(int start, int end) {
if ((start < 0) || (start >= end) || (end > length))
return ("");
else
return (string.substring(start, end));
}
/**
* Return the index of the next occurrence of the specified character,
* or the index of the character after the last position of the string
* if no more occurrences of this character are found. The current
* parsing position is updated to the returned value.
*
* @param ch Character to be found
* @return The character index
*/
public int findChar(char ch) {
while ((index < length) && (ch != chars[index]))
index++;
return (index);
}
/**
* Return the index of the next occurrence of a non-whitespace character,
* or the index of the character after the last position of the string
* if no more non-whitespace characters are found. The current
* parsing position is updated to the returned value.
* @return Return current index after skipping blank characters
*/
public int findText() {
while ((index < length) && isWhite(chars[index]))
index++;
return (index);
}
/**
* Return the index of the next occurrence of a whitespace character,
* or the index of the character after the last position of the string
* if no more whitespace characters are found. The current parsing
* position is updated to the returned value.
*
* @return The next index after skipping the text
*/
public int findWhite() {
while ((index < length) && !isWhite(chars[index]))
index++;
return (index);
}
/**
* Reset the current state of the parser to the beginning of the
* current string being parsed.
*/
public void reset() {
index = 0;
}
/**
* Advance the current parsing position while it is pointing at the
* specified character, or until it moves past the end of the string.
* Return the final value.
*
* @param ch Character to be skipped
* @return The index after skipping the current character
*/
public int skipChar(char ch) {
while ((index < length) && (ch == chars[index]))
index++;
return (index);
}
/**
* Advance the current parsing position while it is pointing at a
* non-whitespace character, or until it moves past the end of the string.
* Return the final value.
* @return The next index after skipping the text
*/
public int skipText() {
while ((index < length) && !isWhite(chars[index]))
index++;
return (index);
}
/**
* Advance the current parsing position while it is pointing at a
* whitespace character, or until it moves past the end of the string.
* Return the final value.
* @return Return current index after skipping blank characters
*/
public int skipWhite() {
while ((index < length) && isWhite(chars[index]))
index++;
return (index);
}
// ------------------------------------------------------ Protected Methods
/**
* Is the specified character considered to be whitespace?
*
* @param ch Character to be checked
* @return Return true, if the character is not blank
*/
protected boolean isWhite(char ch) {
if ((ch == ' ') || (ch == '\t') || (ch == '\r') || (ch == '\n'))
return (true);
else
return (false);
}
}