001: /*
002: * Copyright 2000-2003 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package java.lang;
027:
028: /**
029: * A <tt>CharSequence</tt> is a readable sequence of <code>char</code> values. This
030: * interface provides uniform, read-only access to many different kinds of
031: * <code>char</code> sequences.
032: * A <code>char</code> value represents a character in the <i>Basic
033: * Multilingual Plane (BMP)</i> or a surrogate. Refer to <a
034: * href="Character.html#unicode">Unicode Character Representation</a> for details.
035: *
036: * <p> This interface does not refine the general contracts of the {@link
037: * java.lang.Object#equals(java.lang.Object) equals} and {@link
038: * java.lang.Object#hashCode() hashCode} methods. The result of comparing two
039: * objects that implement <tt>CharSequence</tt> is therefore, in general,
040: * undefined. Each object may be implemented by a different class, and there
041: * is no guarantee that each class will be capable of testing its instances
042: * for equality with those of the other. It is therefore inappropriate to use
043: * arbitrary <tt>CharSequence</tt> instances as elements in a set or as keys in
044: * a map. </p>
045: *
046: * @author Mike McCloskey
047: * @version 1.15 07/05/05
048: * @since 1.4
049: * @spec JSR-51
050: */
051:
052: public interface CharSequence {
053:
054: /**
055: * Returns the length of this character sequence. The length is the number
056: * of 16-bit <code>char</code>s in the sequence.</p>
057: *
058: * @return the number of <code>char</code>s in this sequence
059: */
060: int length();
061:
062: /**
063: * Returns the <code>char</code> value at the specified index. An index ranges from zero
064: * to <tt>length() - 1</tt>. The first <code>char</code> value of the sequence is at
065: * index zero, the next at index one, and so on, as for array
066: * indexing. </p>
067: *
068: * <p>If the <code>char</code> value specified by the index is a
069: * <a href="Character.html#unicode">surrogate</a>, the surrogate
070: * value is returned.
071: *
072: * @param index the index of the <code>char</code> value to be returned
073: *
074: * @return the specified <code>char</code> value
075: *
076: * @throws IndexOutOfBoundsException
077: * if the <tt>index</tt> argument is negative or not less than
078: * <tt>length()</tt>
079: */
080: char charAt(int index);
081:
082: /**
083: * Returns a new <code>CharSequence</code> that is a subsequence of this sequence.
084: * The subsequence starts with the <code>char</code> value at the specified index and
085: * ends with the <code>char</code> value at index <tt>end - 1</tt>. The length
086: * (in <code>char</code>s) of the
087: * returned sequence is <tt>end - start</tt>, so if <tt>start == end</tt>
088: * then an empty sequence is returned. </p>
089: *
090: * @param start the start index, inclusive
091: * @param end the end index, exclusive
092: *
093: * @return the specified subsequence
094: *
095: * @throws IndexOutOfBoundsException
096: * if <tt>start</tt> or <tt>end</tt> are negative,
097: * if <tt>end</tt> is greater than <tt>length()</tt>,
098: * or if <tt>start</tt> is greater than <tt>end</tt>
099: */
100: CharSequence subSequence(int start, int end);
101:
102: /**
103: * Returns a string containing the characters in this sequence in the same
104: * order as this sequence. The length of the string will be the length of
105: * this sequence. </p>
106: *
107: * @return a string consisting of exactly this sequence of characters
108: */
109: public String toString();
110:
111: }
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