/* * Copyright (C) 2009 Google Inc. * * 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 com.google.android.mail.common.base; import static com.google.android.mail.common.base.Preconditions.checkArgument; import static com.google.android.mail.common.base.Preconditions.checkNotNull; import static com.google.android.mail.common.base.Preconditions.checkState; import com.google.common.base.Joiner; import java.util.Iterator; import java.util.NoSuchElementException; import java.util.StringTokenizer; import java.util.regex.Matcher; import java.util.regex.Pattern; import java.util.regex.PatternSyntaxException; /** * An object that divides strings (or other instances of {@code CharSequence}) * into substrings, by recognizing a separator (a.k.a. "delimiter") * which can be expressed as a single character, literal string, regular * expression, {@code CharMatcher}, or by using a fixed substring length. This * class provides the complementary functionality to {@link Joiner}. * *
Here is the most basic example of {@code Splitter} usage:
{@code * * Splitter.on(',').split("foo,bar")}* * This invocation returns an {@code Iterable
By default {@code Splitter}'s behavior is very simplistic:
{@code * * Splitter.on(',').split("foo,,bar, quux")}* * This returns an iterable containing {@code ["foo", "", "bar", " quux"]}. * Notice that the splitter does not assume that you want empty strings removed, * or that you wish to trim whitespace. If you want features like these, simply * ask for them:
{@code * * private static final Splitter MY_SPLITTER = Splitter.on(',') * .trimResults() * .omitEmptyStrings();}* * Now {@code MY_SPLITTER.split("foo, ,bar, quux,")} returns an iterable * containing just {@code ["foo", "bar", "quux"]}. Note that the order in which * the configuration methods are called is never significant; for instance, * trimming is always applied first before checking for an empty result, * regardless of the order in which the {@link #trimResults()} and * {@link #omitEmptyStrings()} methods were invoked. * *
Warning: splitter instances are always immutable; a configuration * method such as {@code omitEmptyStrings} has no effect on the instance it * is invoked on! You must store and use the new splitter instance returned by * the method. This makes splitters thread-safe, and safe to store as {@code * static final} constants (as illustrated above).
{@code * * // Bad! Do not do this! * Splitter splitter = Splitter.on('/'); * splitter.trimResults(); // does nothing! * return splitter.split("wrong / wrong / wrong");}* * The separator recognized by the splitter does not have to be a single * literal character as in the examples above. See the methods {@link * #on(String)}, {@link #on(Pattern)} and {@link #on(CharMatcher)} for examples * of other ways to specify separators. * *
Note: this class does not mimic any of the quirky behaviors of * similar JDK methods; for instance, it does not silently discard trailing * separators, as does {@link String#split(String)}, nor does it have a default * behavior of using five particular whitespace characters as separators, like * {@link StringTokenizer}. * * @author Julien Silland * @author Jesse Wilson * @author Kevin Bourrillion * @since 2009.09.15 tentative */ public final class Splitter { private final CharMatcher trimmer; private final boolean omitEmptyStrings; private final Strategy strategy; private Splitter(Strategy strategy) { this(strategy, false, CharMatcher.NONE); } private Splitter(Strategy strategy, boolean omitEmptyStrings, CharMatcher trimmer) { this.strategy = strategy; this.omitEmptyStrings = omitEmptyStrings; this.trimmer = trimmer; } /** * Returns a splitter that uses the given single-character separator. For * example, {@code Splitter.on(',').split("foo,,bar")} returns an iterable * containing {@code ["foo", "", "bar"]}. * * @param separator the character to recognize as a separator * @return a splitter, with default settings, that recognizes that separator */ public static Splitter on(char separator) { return on(CharMatcher.is(separator)); } /** * Returns a splitter that considers any single character matched by the * given {@code CharMatcher} to be a separator. For example, {@code * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an * iterable containing {@code ["foo", "", "bar", "quux"]}. * * @param separatorMatcher a {@link CharMatcher} that determines whether a * character is a separator * @return a splitter, with default settings, that uses this matcher */ public static Splitter on(final CharMatcher separatorMatcher) { checkNotNull(separatorMatcher); return new Splitter(new Strategy() { /*@Override*/ public SplittingIterator iterator( Splitter splitter, final CharSequence toSplit) { return new SplittingIterator(splitter, toSplit) { @Override int separatorStart(int start) { return separatorMatcher.indexIn(toSplit, start); } @Override int separatorEnd(int separatorPosition) { return separatorPosition + 1; } }; } }); } /** * Returns a splitter that uses the given fixed string as a separator. For * example, {@code Splitter.on(", ").split("foo, bar, baz,qux")} returns an * iterable containing {@code ["foo", "bar", "baz,qux"]}. * * @param separator the literal, nonempty string to recognize as a separator * @return a splitter, with default settings, that recognizes that separator */ public static Splitter on(final String separator) { checkArgument(separator.length() != 0, "The separator may not be the empty string."); return new Splitter(new Strategy() { /*@Override*/ public SplittingIterator iterator( Splitter splitter, CharSequence toSplit) { return new SplittingIterator(splitter, toSplit) { @Override public int separatorStart(int start) { int delimeterLength = separator.length(); positions: for (int p = start, last = toSplit.length() - delimeterLength; p <= last; p++) { for (int i = 0; i < delimeterLength; i++) { if (toSplit.charAt(i + p) != separator.charAt(i)) { continue positions; } } return p; } return -1; } @Override public int separatorEnd(int separatorPosition) { return separatorPosition + separator.length(); } }; } }); } /** * Returns a splitter that considers any subsequence matching {@code * pattern} to be a separator. For example, {@code * Splitter.on(Pattern.compile("\r?\n")).split(entireFile)} splits a string * into lines whether it uses DOS-style or UNIX-style line terminators. * * @param separatorPattern the pattern that determines whether a subsequence * is a separator. This pattern may not match the empty string. * @return a splitter, with default settings, that uses this pattern * @throws IllegalArgumentException if {@code separatorPattern} matches the * empty string */ public static Splitter on(final Pattern separatorPattern) { checkNotNull(separatorPattern); checkArgument(!separatorPattern.matcher("").matches(), "The pattern may not match the empty string: %s", separatorPattern); return new Splitter(new Strategy() { /*@Override*/ public SplittingIterator iterator( final Splitter splitter, CharSequence toSplit) { final Matcher matcher = separatorPattern.matcher(toSplit); return new SplittingIterator(splitter, toSplit) { @Override public int separatorStart(int start) { return matcher.find(start) ? matcher.start() : -1; } @Override public int separatorEnd(int separatorPosition) { return matcher.end(); } }; } }); } /** * Returns a splitter that considers any subsequence matching a given * pattern (regular expression) to be a separator. For example, {@code * Splitter.onPattern("\r?\n").split(entireFile)} splits a string into lines * whether it uses DOS-style or UNIX-style line terminators. This is * equivalent to {@code Splitter.on(Pattern.compile(pattern))}. * * @param separatorPattern the pattern that determines whether a subsequence * is a separator. This pattern may not match the empty string. * @return a splitter, with default settings, that uses this pattern * @throws PatternSyntaxException if {@code separatorPattern} is a malformed * expression * @throws IllegalArgumentException if {@code separatorPattern} matches the * empty string */ public static Splitter onPattern(String separatorPattern) { return on(Pattern.compile(separatorPattern)); } /** * Returns a splitter that divides strings into pieces of the given length. * For example, {@code Splitter.atEach(2).split("abcde")} returns an * iterable containing {@code ["ab", "cd", "e"]}. The last piece can be * smaller than {@code length} but will never be empty. * * @param length the desired length of pieces after splitting * @return a splitter, with default settings, that can split into fixed sized * pieces */ public static Splitter fixedLength(final int length) { checkArgument(length > 0, "The length may not be less than 1"); return new Splitter(new Strategy() { /*@Override*/ public SplittingIterator iterator( final Splitter splitter, CharSequence toSplit) { return new SplittingIterator(splitter, toSplit) { @Override public int separatorStart(int start) { int nextChunkStart = start + length; return (nextChunkStart < toSplit.length() ? nextChunkStart : -1); } @Override public int separatorEnd(int separatorPosition) { return separatorPosition; } }; } }); } /** * Returns a splitter that behaves equivalently to {@code this} splitter, but * automatically omits empty strings from the results. For example, {@code * Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,")} returns an * iterable containing only {@code ["a", "b", "c"]}. * *
If either {@code trimResults} option is also specified when creating a * splitter, that splitter always trims results first before checking for * emptiness. So, for example, {@code * Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ")} returns * an empty iterable. * *
Note that it is ordinarily not possible for {@link #split(CharSequence)}
* to return an empty iterable, but when using this option, it can (if the
* input sequence consists of nothing but separators).
*
* @return a splitter with the desired configuration
*/
public Splitter omitEmptyStrings() {
return new Splitter(strategy, true, trimmer);
}
/**
* Returns a splitter that behaves equivalently to {@code this} splitter, but
* automatically removes leading and trailing {@linkplain
* CharMatcher#WHITESPACE whitespace} from each returned substring; equivalent
* to {@code trimResults(CharMatcher.WHITESPACE)}. For example, {@code
* Splitter.on(',').trimResults().split(" a, b ,c ")} returns an iterable
* containing {@code ["a", "b", "c"]}.
*
* @return a splitter with the desired configuration
*/
public Splitter trimResults() {
return trimResults(CharMatcher.WHITESPACE);
}
/**
* Returns a splitter that behaves equivalently to {@code this} splitter, but
* removes all leading or trailing characters matching the given {@code
* CharMatcher} from each returned substring. For example, {@code
* Splitter.on(',').trimResults(CharMatcher.is('_')).split("_a ,_b_ ,c__")}
* returns an iterable containing {@code ["a ", "b_ ", "c"]}.
*
* @param trimmer a {@link CharMatcher} that determines whether a character
* should be removed from the beginning/end of a subsequence
* @return a splitter with the desired configuration
*/
public Splitter trimResults(CharMatcher trimmer) {
checkNotNull(trimmer);
return new Splitter(strategy, omitEmptyStrings, trimmer);
}
/**
* Splits the {@link CharSequence} passed in parameter.
*
* @param sequence the sequence of characters to split
* @return an iteration over the segments split from the parameter.
*/
public Iterable