FYC: 7197183 : Provide CharSequence.subSequenceView which allows for sub-sequence views of character sequences. (original) (raw)

Thu Jul 17 00:09:29 UTC 2014

* Provides a sub-sequence view on a character sequence. Changes in the
* source will be reflected in the sub-sequence. The sub-sequence must, at
* all times, be a proper sub-sequence of the source character sequence.
*
* @since 1.9
*/
   private final CharSequence source;
   private final int fromInclusive;
   private final IntSupplier toExclusive;
   CharSubSequenceView(CharSequence source, int fromInclusive, int toExclusive) {
       this(source, fromInclusive, () -> toExclusive);
   }
   CharSubSequenceView(CharSequence source, int fromInclusive, IntSupplier toExclusive) {
       this.source = Objects.requireNonNull(source);
       if(fromInclusive < 0 || fromInclusive >= source.length() ||
          toExclusive.getAsInt() < fromInclusive || toExclusive.getAsInt() > source.length()) {
           throw new IllegalArgumentException("Invalid index");
       }
       this.fromInclusive = fromInclusive;
       this.toExclusive = toExclusive;
   }
   @Override
   public int length() {
       return toExclusive.getAsInt() - fromInclusive;
   }
   @Override
   public char charAt(int index) {
       if(index >= length()) {
           throw new IllegalArgumentException("Invalid Index");
       }
       //
       return source.charAt(fromInclusive + index);
   }
   @Override
   public CharSequence subSequence(int start, int end) {
      if (end > length()) {
          throw new IllegalArgumentException("Invalid Index");
      }
      return source.subSequence(fromInclusive + start, fromInclusive + end);
   }
   @Override
   public String toString() {
       int len = length();
       char[] chars = new char[len];
       for(int each = 0; each < len; each++) {
           chars[each] = charAt(each);
       }
       return new String(chars, true);
   }
* Returns as a character sequence the specified sub-sequence view of the
* provided source character sequence. Changes in the source will be
* reflected in the sub-sequence. The sub-sequence must, at all times, be
* a proper sub-sequence of the source character sequence.
*
* @param source The character sequence from which the sub-sequence is
* derived.
* @param startInclusive The index of the character in the source character
* sequence which will be the first character in the sub-sequence.
* @param endExclusive The index after the last the character in the source
* character sequence which will be the last character in the sub-sequence
* @return the character sub-sequence.
* @since 1.9
*/
   return new CharSubSequenceView(source, startInclusive, endExclusive);
* Returns as a character sequence the specified sub-sequence view of the
* provided source character sequence. Changes in the source will be
* reflected in the sub-sequence. The sub-sequence must, at all times, be
* a proper sub-sequence of the source character sequence. This variation
* allows for the size of the sub-sequence to vary, usually to follow the
* size of a growing character sequence.
*
* @apiNote The most common usage of this subSequence is to follow changes
* in the size of the source.
* {@code
* StringBuilder source = new StringBuilder("prefix:");
* CharSeqence toEnd = CharSequence.subSequence(source, 7, source::length);
* }
* In this example the value of {@code toEnd} will always be a sub-sequence
* of {@code source} but will omit the first 7 characters.
*
* @param source The character sequence from which the sub-sequence is
* derived.
* @param startInclusive The index of the character in the source character
* sequence which will be the first character in the sub-sequence.
* @param endExclusive A supplier which returns the index after the last the
* character in the source character sequence which will be the last
* character in the sub-sequence
* @return the character sub-sequence.
* @since 1.9
*/
   return new CharSubSequenceView(source, startInclusive, endExclusive);