/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 java.lang;


/**
 * This interface represents an ordered set of characters and defines the
 * methods to probe them.
 */
public interface CharSequence {

    /**
     * Returns the number of characters in this sequence.
     * 
     * @return the number of characters.
     */
    public int length();

    /**
     * Returns the character at the specified index, with the first character
     * having index zero.
     * 
     * @param index
     *            the index of the character to return.
     * @return the requested character.
     * @throws IndexOutOfBoundsException
     *             if {@code index < 0} or {@code index} is greater than the
     *             length of this sequence.
     */
    public char charAt(int index);

    /**
     * Returns a {@code CharSequence} from the {@code start} index (inclusive)
     * to the {@code end} index (exclusive) of this sequence.
     * 
     * @param start
     *            the start offset of the sub-sequence. It is inclusive, that
     *            is, the index of the first character that is included in the
     *            sub-sequence.
     * @param end
     *            the end offset of the sub-sequence. It is exclusive, that is,
     *            the index of the first character after those that are included
     *            in the sub-sequence
     * @return the requested sub-sequence.
     * @throws IndexOutOfBoundsException
     *             if {@code start < 0}, {@code end < 0}, {@code start > end},
     *             or if {@code start} or {@code end} are greater than the
     *             length of this sequence.
     */
    public CharSequence subSequence(int start, int end);

    /**
     * Returns a string with the same characters in the same order as in this
     * sequence.
     * 
     * @return a string based on this sequence.
     */
    public String toString();
}