source: trunk/gcc/libjava/java/lang/CharSequence.java

/* CharSequence.java -- Anything that has an indexed sequence of chars
   Copyright (C) 2001, 2002 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.

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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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package java.lang;

/**
 * General functions on a sequence of chars. This interface is implemented
 * by <code>String</code>, <code>StringBuffer</code> and
 * <code>CharBuffer</code> to give a uniform way to get chars at a certain
 * index, the number of characters in the sequence and a subrange of the
 * chars. Indexes start at 0 and the last index is <code>length()-1</code>.
 *
 * <p>Even when classes implement this interface they are not always
 * exchangeble because they might implement their compare, equals or hash
 * function differently. This means that in general one should not use a
 * <code>CharSequence</code> as keys in collections since two sequences
 * with the same chars at the same indexes with the same length might not
 * have the same hash code, be equal or be comparable since the are
 * represented by different classes.
 *
 * @author Mark Wielaard (mark@klomp.org)
 * @since 1.4
 * @status updated to 1.4
 */
public interface CharSequence
{
  /**
   * Returns the character at the given index.
   *
   * @param i the index to retrieve from
   * @return the character at that location
   * @throws IndexOutOfBoundsException if i &lt; 0 || i &gt;= length() - 1
   */
  char charAt(int i);

  /**
   * Returns the length of the sequence. This is the number of 16-bit
   * characters in the sequence, which may differ from the length of the
   * underlying encoding.
   *
   * @return the sequence length
   */
  int length();

  /**
   * Returns a new <code>CharSequence</char> of the indicated range.
   *
   * @param begin the start index (inclusive)
   * @param end the end index (exclusive)
   * @return a subsequence of this
   * @throws IndexOutOfBoundsException if begin &gt; end || begin &lt; 0 ||
   *         end &gt; length()
   */
  CharSequence subSequence(int begin, int end);

  /**
   * Returns the complete <code>CharSequence</code> as a <code>String</code>.
   * Classes that implement this interface should return a <code>String</code>
   * which contains only the characters in the sequence in the correct order.
   *
   * @return the character sequence as a String
   */
  String toString();
}