guava/src/com/google/common/base/Splitter.java - platform/external/guava - Git at Google

 /*
  * Copyright (C) 2009 The Guava Authors
  *
  * 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.common.base;

 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;

 import com.google.common.annotations.Beta;
 import com.google.common.annotations.GwtCompatible;
 import com.google.common.annotations.GwtIncompatible;

 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 import javax.annotation.CheckReturnValue;

 /**
  * Extracts non-overlapping substrings from an input string, typically by
  * recognizing appearances of a <i>separator</i> sequence. This separator can be
  * specified as a single {@linkplain #on(char) character}, fixed {@linkplain
  * #on(String) string}, {@linkplain #onPattern regular expression} or {@link
  * #on(CharMatcher) CharMatcher} instance. Or, instead of using a separator at
  * all, a splitter can extract adjacent substrings of a given {@linkplain
  * #fixedLength fixed length}.
  *
  * <p>For example, this expression: <pre>   {@code
  *
  *   Splitter.on(',').split("foo,bar,qux")}</pre>
  *
  * ... produces an {@code Iterable} containing {@code "foo"}, {@code "bar"} and
  * {@code "qux"}, in that order.
  *
  * <p>By default, {@code Splitter}'s behavior is simplistic and unassuming. The
  * following expression: <pre>   {@code
  *
  *   Splitter.on(',').split(" foo,,,  bar ,")}</pre>
  *
  * ... yields the substrings {@code [" foo", "", "", "  bar ", ""]}. If this
  * is not the desired behavior, use configuration methods to obtain a <i>new</i>
  * splitter instance with modified behavior: <pre>   {@code
  *
  *   private static final Splitter MY_SPLITTER = Splitter.on(',')
  *       .trimResults()
  *       .omitEmptyStrings();}</pre>
  *
  * <p>Now {@code MY_SPLITTER.split("foo,,,  bar ,")} returns just {@code ["foo",
  * "bar"]}. Note that the order in which these configuration methods are called
  * is never significant.
  *
  * <p><b>Warning:</b> Splitter instances are immutable. Invoking a configuration
  * method has no effect on the receiving instance; you must store and use the
  * new splitter instance it returns instead. <pre>   {@code
  *
  *   // Do NOT do this
  *   Splitter splitter = Splitter.on('/');
  *   splitter.trimResults(); // does nothing!
  *   return splitter.split("wrong / wrong / wrong");}</pre>
  *
  * <p>For separator-based splitters that do not use {@code omitEmptyStrings}, an
  * input string containing {@code n} occurrences of the separator naturally
  * yields an iterable of size {@code n + 1}. So if the separator does not occur
  * anywhere in the input, a single substring is returned containing the entire
  * input. Consequently, all splitters split the empty string to {@code [""]}
  * (note: even fixed-length splitters).
  *
  * <p>Splitter instances are thread-safe immutable, and are therefore safe to
  * store as {@code static final} constants.
  *
  * <p>The {@link Joiner} class provides the inverse operation to splitting, but
  * note that a round-trip between the two should be assumed to be lossy.
  *
  * <p>See the Guava User Guide article on <a href=
  * "http://code.google.com/p/guava-libraries/wiki/StringsExplained#Splitter">
  * {@code Splitter}</a>.
  *
  * @author Julien Silland
  * @author Jesse Wilson
  * @author Kevin Bourrillion
  * @author Louis Wasserman
  * @since 1.0
  */
 @GwtCompatible(emulated = true)
 public final class Splitter {
   private final CharMatcher trimmer;
   private final boolean omitEmptyStrings;
   private final Strategy strategy;
   private final int limit;

   private Splitter(Strategy strategy) {
     this(strategy, false, CharMatcher.NONE, Integer.MAX_VALUE);
   }

   private Splitter(Strategy strategy, boolean omitEmptyStrings,
       CharMatcher trimmer, int limit) {
     this.strategy = strategy;
     this.omitEmptyStrings = omitEmptyStrings;
     this.trimmer = trimmer;
     this.limit = limit;
   }

   /**
    * 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")} returns an
    * iterable containing {@code ["foo", "bar,baz"]}.
    *
    * @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 separatorLength = separator.length();

             positions:
             for (int p = start, last = toSplit.length() - separatorLength;
                 p <= last; p++) {
               for (int i = 0; i < separatorLength; 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
    */
   @GwtIncompatible("java.util.regex")
   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 java.util.regex.PatternSyntaxException if {@code separatorPattern}
    *     is a malformed expression
    * @throws IllegalArgumentException if {@code separatorPattern} matches the
    *     empty string
    */
   @GwtIncompatible("java.util.regex")
   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.fixedLength(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.
    *
    * <p><b>Exception:</b> for consistency with separator-based splitters, {@code
    * split("")} does not yield an empty iterable, but an iterable containing
    * {@code ""}. This is the only case in which {@code
    * Iterables.size(split(input))} does not equal {@code
    * IntMath.divide(input.length(), length, CEILING)}. To avoid this behavior,
    * use {@code omitEmptyStrings}.
    *
    * @param length the desired length of pieces after splitting, a positive
    *     integer
    * @return a splitter, with default settings, that can split into fixed sized
    *     pieces
    * @throws IllegalArgumentException if {@code length} is zero or negative
    */
   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"]}.
    *
    * <p>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.
    *
    * <p>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
    */
   @CheckReturnValue
   public Splitter omitEmptyStrings() {
     return new Splitter(strategy, true, trimmer, limit);
   }

   /**
    * Returns a splitter that behaves equivalently to {@code this} splitter but
    * stops splitting after it reaches the limit.
    * The limit defines the maximum number of items returned by the iterator.
    *
    * <p>For example,
    * {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable
    * containing {@code ["a", "b", "c,d"]}.  When omitting empty strings, the
    * omitted strings do no count.  Hence,
    * {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")}
    * returns an iterable containing {@code ["a", "b", "c,d"}.
    * When trim is requested, all entries, including the last are trimmed.  Hence
    * {@code Splitter.on(',').limit(3).trimResults().split(" a , b , c , d ")}
    * results in @{code ["a", "b", "c , d"]}.
    *
    * @param limit the maximum number of items returns
    * @return a splitter with the desired configuration
    * @since 9.0
    */
   @CheckReturnValue
   public Splitter limit(int limit) {
     checkArgument(limit > 0, "must be greater than zero: %s", limit);
     return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
   }

   /**
    * 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
    */
   @CheckReturnValue
   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
    */
   // TODO(kevinb): throw if a trimmer was already specified!
   @CheckReturnValue
   public Splitter trimResults(CharMatcher trimmer) {
     checkNotNull(trimmer);
     return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
   }

   /**
    * Splits {@code sequence} into string components and makes them available
    * through an {@link Iterator}, which may be lazily evaluated. If you want
    * an eagerly computed {@link List}, use {@link #splitToList(CharSequence)}.
    *
    * @param sequence the sequence of characters to split
    * @return an iteration over the segments split from the parameter.
    */
   public Iterable<String> split(final CharSequence sequence) {
     checkNotNull(sequence);

     return new Iterable<String>() {
       @Override public Iterator<String> iterator() {
         return splittingIterator(sequence);
       }
       @Override public String toString() {
         return Joiner.on(", ")
             .appendTo(new StringBuilder().append('['), this)
             .append(']')
             .toString();
       }
     };
   }

   private Iterator<String> splittingIterator(CharSequence sequence) {
     return strategy.iterator(this, sequence);
   }

   /**
    * Splits {@code sequence} into string components and returns them as
    * an immutable list. If you want an {@link Iterable} which may be lazily
    * evaluated, use {@link #split(CharSequence)}.
    *
    * @param sequence the sequence of characters to split
    * @return an immutable list of the segments split from the parameter
    * @since 15.0
    */
   @Beta
   public List<String> splitToList(CharSequence sequence) {
     checkNotNull(sequence);

     Iterator<String> iterator = splittingIterator(sequence);
     List<String> result = new ArrayList<String>();

     while (iterator.hasNext()) {
       result.add(iterator.next());
     }

     return Collections.unmodifiableList(result);
   }

   /**
    * Returns a {@code MapSplitter} which splits entries based on this splitter,
    * and splits entries into keys and values using the specified separator.
    *
    * @since 10.0
    */
   @CheckReturnValue
   @Beta
   public MapSplitter withKeyValueSeparator(String separator) {
     return withKeyValueSeparator(on(separator));
   }

   /**
    * Returns a {@code MapSplitter} which splits entries based on this splitter,
    * and splits entries into keys and values using the specified separator.
    *
    * @since 14.0
    */
   @CheckReturnValue
   @Beta
   public MapSplitter withKeyValueSeparator(char separator) {
     return withKeyValueSeparator(on(separator));
   }

   /**
    * Returns a {@code MapSplitter} which splits entries based on this splitter,
    * and splits entries into keys and values using the specified key-value
    * splitter.
    *
    * @since 10.0
    */
   @CheckReturnValue
   @Beta
   public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) {
     return new MapSplitter(this, keyValueSplitter);
   }

   /**
    * An object that splits strings into maps as {@code Splitter} splits
    * iterables and lists. Like {@code Splitter}, it is thread-safe and
    * immutable.
    *
    * @since 10.0
    */
   @Beta
   public static final class MapSplitter {
     private static final String INVALID_ENTRY_MESSAGE =
         "Chunk [%s] is not a valid entry";
     private final Splitter outerSplitter;
     private final Splitter entrySplitter;

     private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) {
       this.outerSplitter = outerSplitter; // only "this" is passed
       this.entrySplitter = checkNotNull(entrySplitter);
     }

     /**
      * Splits {@code sequence} into substrings, splits each substring into
      * an entry, and returns an unmodifiable map with each of the entries. For
      * example, <code>
      * Splitter.on(';').trimResults().withKeyValueSeparator("=>")
      * .split("a=>b ; c=>b")
      * </code> will return a mapping from {@code "a"} to {@code "b"} and
      * {@code "c"} to {@code b}.
      *
      * <p>The returned map preserves the order of the entries from
      * {@code sequence}.
      *
      * @throws IllegalArgumentException if the specified sequence does not split
      *         into valid map entries, or if there are duplicate keys
      */
     public Map<String, String> split(CharSequence sequence) {
       Map<String, String> map = new LinkedHashMap<String, String>();
       for (String entry : outerSplitter.split(sequence)) {
         Iterator<String> entryFields = entrySplitter.splittingIterator(entry);

         checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
         String key = entryFields.next();
         checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key);

         checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
         String value = entryFields.next();
         map.put(key, value);

         checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
       }
       return Collections.unmodifiableMap(map);
     }
   }

   private interface Strategy {
     Iterator<String> iterator(Splitter splitter, CharSequence toSplit);
   }

   private abstract static class SplittingIterator extends AbstractIterator<String> {
     final CharSequence toSplit;
     final CharMatcher trimmer;
     final boolean omitEmptyStrings;

     /**
      * Returns the first index in {@code toSplit} at or after {@code start}
      * that contains the separator.
      */
     abstract int separatorStart(int start);

     /**
      * Returns the first index in {@code toSplit} after {@code
      * separatorPosition} that does not contain a separator. This method is only
      * invoked after a call to {@code separatorStart}.
      */
     abstract int separatorEnd(int separatorPosition);

     int offset = 0;
     int limit;

     protected SplittingIterator(Splitter splitter, CharSequence toSplit) {
       this.trimmer = splitter.trimmer;
       this.omitEmptyStrings = splitter.omitEmptyStrings;
       this.limit = splitter.limit;
       this.toSplit = toSplit;
     }

     @Override protected String computeNext() {
       /*
        * The returned string will be from the end of the last match to the
        * beginning of the next one. nextStart is the start position of the
        * returned substring, while offset is the place to start looking for a
        * separator.
        */
       int nextStart = offset;
       while (offset != -1) {
         int start = nextStart;
         int end;

         int separatorPosition = separatorStart(offset);
         if (separatorPosition == -1) {
           end = toSplit.length();
           offset = -1;
         } else {
           end = separatorPosition;
           offset = separatorEnd(separatorPosition);
         }
         if (offset == nextStart) {
           /*
            * This occurs when some pattern has an empty match, even if it
            * doesn't match the empty string -- for example, if it requires
            * lookahead or the like. The offset must be increased to look for
            * separators beyond this point, without changing the start position
            * of the next returned substring -- so nextStart stays the same.
            */
           offset++;
           if (offset >= toSplit.length()) {
             offset = -1;
           }
           continue;
         }

         while (start < end && trimmer.matches(toSplit.charAt(start))) {
           start++;
         }
         while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
           end--;
         }

         if (omitEmptyStrings && start == end) {
           // Don't include the (unused) separator in next split string.
           nextStart = offset;
           continue;
         }

         if (limit == 1) {
           // The limit has been reached, return the rest of the string as the
           // final item.  This is tested after empty string removal so that
           // empty strings do not count towards the limit.
           end = toSplit.length();
           offset = -1;
           // Since we may have changed the end, we need to trim it again.
           while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
             end--;
           }
         } else {
           limit--;
         }

         return toSplit.subSequence(start, end).toString();
       }
       return endOfData();
     }
   }
 }
	/*
	* Copyright (C) 2009 The Guava Authors
	*
	* 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.common.base;

	import static com.google.common.base.Preconditions.checkArgument;
	import static com.google.common.base.Preconditions.checkNotNull;

	import com.google.common.annotations.Beta;
	import com.google.common.annotations.GwtCompatible;
	import com.google.common.annotations.GwtIncompatible;

	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Iterator;
	import java.util.LinkedHashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.regex.Matcher;
	import java.util.regex.Pattern;

	import javax.annotation.CheckReturnValue;

	/**
	* Extracts non-overlapping substrings from an input string, typically by
	* recognizing appearances of a <i>separator</i> sequence. This separator can be
	* specified as a single {@linkplain #on(char) character}, fixed {@linkplain
	* #on(String) string}, {@linkplain #onPattern regular expression} or {@link
	* #on(CharMatcher) CharMatcher} instance. Or, instead of using a separator at
	* all, a splitter can extract adjacent substrings of a given {@linkplain
	* #fixedLength fixed length}.
	*
	* <p>For example, this expression: <pre> {@code
	*
	* Splitter.on(',').split("foo,bar,qux")}</pre>
	*
	* ... produces an {@code Iterable} containing {@code "foo"}, {@code "bar"} and
	* {@code "qux"}, in that order.
	*
	* <p>By default, {@code Splitter}'s behavior is simplistic and unassuming. The
	* following expression: <pre> {@code
	*
	* Splitter.on(',').split(" foo,,, bar ,")}</pre>
	*
	* ... yields the substrings {@code [" foo", "", "", " bar ", ""]}. If this
	* is not the desired behavior, use configuration methods to obtain a <i>new</i>
	* splitter instance with modified behavior: <pre> {@code
	*
	* private static final Splitter MY_SPLITTER = Splitter.on(',')
	* .trimResults()
	* .omitEmptyStrings();}</pre>
	*
	* <p>Now {@code MY_SPLITTER.split("foo,,, bar ,")} returns just {@code ["foo",
	* "bar"]}. Note that the order in which these configuration methods are called
	* is never significant.
	*
	* <p><b>Warning:</b> Splitter instances are immutable. Invoking a configuration
	* method has no effect on the receiving instance; you must store and use the
	* new splitter instance it returns instead. <pre> {@code
	*
	* // Do NOT do this
	* Splitter splitter = Splitter.on('/');
	* splitter.trimResults(); // does nothing!
	* return splitter.split("wrong / wrong / wrong");}</pre>
	*
	* <p>For separator-based splitters that do not use {@code omitEmptyStrings}, an
	* input string containing {@code n} occurrences of the separator naturally
	* yields an iterable of size {@code n + 1}. So if the separator does not occur
	* anywhere in the input, a single substring is returned containing the entire
	* input. Consequently, all splitters split the empty string to {@code [""]}
	* (note: even fixed-length splitters).
	*
	* <p>Splitter instances are thread-safe immutable, and are therefore safe to
	* store as {@code static final} constants.
	*
	* <p>The {@link Joiner} class provides the inverse operation to splitting, but
	* note that a round-trip between the two should be assumed to be lossy.
	*
	* <p>See the Guava User Guide article on <a href=
	* "http://code.google.com/p/guava-libraries/wiki/StringsExplained#Splitter">
	* {@code Splitter}</a>.
	*
	* @author Julien Silland
	* @author Jesse Wilson
	* @author Kevin Bourrillion
	* @author Louis Wasserman
	* @since 1.0
	*/
	@GwtCompatible(emulated = true)
	public final class Splitter {
	private final CharMatcher trimmer;
	private final boolean omitEmptyStrings;
	private final Strategy strategy;
	private final int limit;

	private Splitter(Strategy strategy) {
	this(strategy, false, CharMatcher.NONE, Integer.MAX_VALUE);
	}

	private Splitter(Strategy strategy, boolean omitEmptyStrings,
	CharMatcher trimmer, int limit) {
	this.strategy = strategy;
	this.omitEmptyStrings = omitEmptyStrings;
	this.trimmer = trimmer;
	this.limit = limit;
	}

	/**
	* 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")} returns an
	* iterable containing {@code ["foo", "bar,baz"]}.
	*
	* @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 separatorLength = separator.length();

	positions:
	for (int p = start, last = toSplit.length() - separatorLength;
	p <= last; p++) {
	for (int i = 0; i < separatorLength; 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
	*/
	@GwtIncompatible("java.util.regex")
	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 java.util.regex.PatternSyntaxException if {@code separatorPattern}
	* is a malformed expression
	* @throws IllegalArgumentException if {@code separatorPattern} matches the
	* empty string
	*/
	@GwtIncompatible("java.util.regex")
	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.fixedLength(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.
	*
	* <p><b>Exception:</b> for consistency with separator-based splitters, {@code
	* split("")} does not yield an empty iterable, but an iterable containing
	* {@code ""}. This is the only case in which {@code
	* Iterables.size(split(input))} does not equal {@code
	* IntMath.divide(input.length(), length, CEILING)}. To avoid this behavior,
	* use {@code omitEmptyStrings}.
	*
	* @param length the desired length of pieces after splitting, a positive
	* integer
	* @return a splitter, with default settings, that can split into fixed sized
	* pieces
	* @throws IllegalArgumentException if {@code length} is zero or negative
	*/
	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"]}.
	*
	* <p>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.
	*
	* <p>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
	*/
	@CheckReturnValue
	public Splitter omitEmptyStrings() {
	return new Splitter(strategy, true, trimmer, limit);
	}

	/**
	* Returns a splitter that behaves equivalently to {@code this} splitter but
	* stops splitting after it reaches the limit.
	* The limit defines the maximum number of items returned by the iterator.
	*
	* <p>For example,
	* {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable
	* containing {@code ["a", "b", "c,d"]}. When omitting empty strings, the
	* omitted strings do no count. Hence,
	* {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")}
	* returns an iterable containing {@code ["a", "b", "c,d"}.
	* When trim is requested, all entries, including the last are trimmed. Hence
	* {@code Splitter.on(',').limit(3).trimResults().split(" a , b , c , d ")}
	* results in @{code ["a", "b", "c , d"]}.
	*
	* @param limit the maximum number of items returns
	* @return a splitter with the desired configuration
	* @since 9.0
	*/
	@CheckReturnValue
	public Splitter limit(int limit) {
	checkArgument(limit > 0, "must be greater than zero: %s", limit);
	return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
	}

	/**
	* 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
	*/
	@CheckReturnValue
	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
	*/
	// TODO(kevinb): throw if a trimmer was already specified!
	@CheckReturnValue
	public Splitter trimResults(CharMatcher trimmer) {
	checkNotNull(trimmer);
	return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
	}

	/**
	* Splits {@code sequence} into string components and makes them available
	* through an {@link Iterator}, which may be lazily evaluated. If you want
	* an eagerly computed {@link List}, use {@link #splitToList(CharSequence)}.
	*
	* @param sequence the sequence of characters to split
	* @return an iteration over the segments split from the parameter.
	*/
	public Iterable<String> split(final CharSequence sequence) {
	checkNotNull(sequence);

	return new Iterable<String>() {
	@Override public Iterator<String> iterator() {
	return splittingIterator(sequence);
	}
	@Override public String toString() {
	return Joiner.on(", ")
	.appendTo(new StringBuilder().append('['), this)
	.append(']')
	.toString();
	}
	};
	}

	private Iterator<String> splittingIterator(CharSequence sequence) {
	return strategy.iterator(this, sequence);
	}

	/**
	* Splits {@code sequence} into string components and returns them as
	* an immutable list. If you want an {@link Iterable} which may be lazily
	* evaluated, use {@link #split(CharSequence)}.
	*
	* @param sequence the sequence of characters to split
	* @return an immutable list of the segments split from the parameter
	* @since 15.0
	*/
	@Beta
	public List<String> splitToList(CharSequence sequence) {
	checkNotNull(sequence);

	Iterator<String> iterator = splittingIterator(sequence);
	List<String> result = new ArrayList<String>();

	while (iterator.hasNext()) {
	result.add(iterator.next());
	}

	return Collections.unmodifiableList(result);
	}

	/**
	* Returns a {@code MapSplitter} which splits entries based on this splitter,
	* and splits entries into keys and values using the specified separator.
	*
	* @since 10.0
	*/
	@CheckReturnValue
	@Beta
	public MapSplitter withKeyValueSeparator(String separator) {
	return withKeyValueSeparator(on(separator));
	}

	/**
	* Returns a {@code MapSplitter} which splits entries based on this splitter,
	* and splits entries into keys and values using the specified separator.
	*
	* @since 14.0
	*/
	@CheckReturnValue
	@Beta
	public MapSplitter withKeyValueSeparator(char separator) {
	return withKeyValueSeparator(on(separator));
	}

	/**
	* Returns a {@code MapSplitter} which splits entries based on this splitter,
	* and splits entries into keys and values using the specified key-value
	* splitter.
	*
	* @since 10.0
	*/
	@CheckReturnValue
	@Beta
	public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) {
	return new MapSplitter(this, keyValueSplitter);
	}

	/**
	* An object that splits strings into maps as {@code Splitter} splits
	* iterables and lists. Like {@code Splitter}, it is thread-safe and
	* immutable.
	*
	* @since 10.0
	*/
	@Beta
	public static final class MapSplitter {
	private static final String INVALID_ENTRY_MESSAGE =
	"Chunk [%s] is not a valid entry";
	private final Splitter outerSplitter;
	private final Splitter entrySplitter;

	private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) {
	this.outerSplitter = outerSplitter; // only "this" is passed
	this.entrySplitter = checkNotNull(entrySplitter);
	}

	/**
	* Splits {@code sequence} into substrings, splits each substring into
	* an entry, and returns an unmodifiable map with each of the entries. For
	* example, <code>
	* Splitter.on(';').trimResults().withKeyValueSeparator("=>")
	* .split("a=>b ; c=>b")
	* </code> will return a mapping from {@code "a"} to {@code "b"} and
	* {@code "c"} to {@code b}.
	*
	* <p>The returned map preserves the order of the entries from
	* {@code sequence}.
	*
	* @throws IllegalArgumentException if the specified sequence does not split
	* into valid map entries, or if there are duplicate keys
	*/
	public Map<String, String> split(CharSequence sequence) {
	Map<String, String> map = new LinkedHashMap<String, String>();
	for (String entry : outerSplitter.split(sequence)) {
	Iterator<String> entryFields = entrySplitter.splittingIterator(entry);

	checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
	String key = entryFields.next();
	checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key);

	checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
	String value = entryFields.next();
	map.put(key, value);

	checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
	}
	return Collections.unmodifiableMap(map);
	}
	}

	private interface Strategy {
	Iterator<String> iterator(Splitter splitter, CharSequence toSplit);
	}

	private abstract static class SplittingIterator extends AbstractIterator<String> {
	final CharSequence toSplit;
	final CharMatcher trimmer;
	final boolean omitEmptyStrings;

	/**
	* Returns the first index in {@code toSplit} at or after {@code start}
	* that contains the separator.
	*/
	abstract int separatorStart(int start);

	/**
	* Returns the first index in {@code toSplit} after {@code
	* separatorPosition} that does not contain a separator. This method is only
	* invoked after a call to {@code separatorStart}.
	*/
	abstract int separatorEnd(int separatorPosition);

	int offset = 0;
	int limit;

	protected SplittingIterator(Splitter splitter, CharSequence toSplit) {
	this.trimmer = splitter.trimmer;
	this.omitEmptyStrings = splitter.omitEmptyStrings;
	this.limit = splitter.limit;
	this.toSplit = toSplit;
	}

	@Override protected String computeNext() {
	/*
	* The returned string will be from the end of the last match to the
	* beginning of the next one. nextStart is the start position of the
	* returned substring, while offset is the place to start looking for a
	* separator.
	*/
	int nextStart = offset;
	while (offset != -1) {
	int start = nextStart;
	int end;

	int separatorPosition = separatorStart(offset);
	if (separatorPosition == -1) {
	end = toSplit.length();
	offset = -1;
	} else {
	end = separatorPosition;
	offset = separatorEnd(separatorPosition);
	}
	if (offset == nextStart) {
	/*
	* This occurs when some pattern has an empty match, even if it
	* doesn't match the empty string -- for example, if it requires
	* lookahead or the like. The offset must be increased to look for
	* separators beyond this point, without changing the start position
	* of the next returned substring -- so nextStart stays the same.
	*/
	offset++;
	if (offset >= toSplit.length()) {
	offset = -1;
	}
	continue;
	}

	while (start < end && trimmer.matches(toSplit.charAt(start))) {
	start++;
	}
	while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
	end--;
	}

	if (omitEmptyStrings && start == end) {
	// Don't include the (unused) separator in next split string.
	nextStart = offset;
	continue;
	}

	if (limit == 1) {
	// The limit has been reached, return the rest of the string as the
	// final item. This is tested after empty string removal so that
	// empty strings do not count towards the limit.
	end = toSplit.length();
	offset = -1;
	// Since we may have changed the end, we need to trim it again.
	while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
	end--;
	}
	} else {
	limit--;
	}

	return toSplit.subSequence(start, end).toString();
	}
	return endOfData();
	}
	}
	}