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Java example source code file (CharSequenceUtils.java)

This example Java source code file (CharSequenceUtils.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

charsequence, charsequenceutils, not_found, string

The CharSequenceUtils.java Java example source code

/*
 * 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 org.apache.commons.lang3;

/**
 * <p>Operations on {@link CharSequence} that are
 * {@code null} safe.</p>
 *
 * @see CharSequence
 * @since 3.0
 */
public class CharSequenceUtils {

    private static final int NOT_FOUND = -1;

    /**
     * <p>{@code CharSequenceUtils} instances should NOT be constructed in
     * standard programming. </p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public CharSequenceUtils() {
        super();
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Returns a new {@code CharSequence} that is a subsequence of this
     * sequence starting with the {@code char} value at the specified index.</p>
     *
     * <p>This provides the {@code CharSequence} equivalent to {@link String#substring(int)}.
     * The length (in {@code char}) of the returned sequence is {@code length() - start},
     * so if {@code start == end} then an empty sequence is returned.</p>
     *
     * @param cs  the specified subsequence, null returns null
     * @param start  the start index, inclusive, valid
     * @return a new subsequence, may be null
     * @throws IndexOutOfBoundsException if {@code start} is negative or if 
     *  {@code start} is greater than {@code length()}
     */
    public static CharSequence subSequence(final CharSequence cs, final int start) {
        return cs == null ? null : cs.subSequence(start, cs.length());
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Finds the first index in the {@code CharSequence} that matches the
     * specified character.</p>
     *
     * @param cs  the {@code CharSequence} to be processed, not null
     * @param searchChar  the char to be searched for
     * @param start  the start index, negative starts at the string start
     * @return the index where the search char was found, -1 if not found
     */
    static int indexOf(final CharSequence cs, final int searchChar, int start) {
        if (cs instanceof String) {
            return ((String) cs).indexOf(searchChar, start);
        }
        final int sz = cs.length();
        if (start < 0) {
            start = 0;
        }
        for (int i = start; i < sz; i++) {
            if (cs.charAt(i) == searchChar) {
                return i;
            }
        }
        return NOT_FOUND;
    }

    /**
     * Used by the indexOf(CharSequence methods) as a green implementation of indexOf.
     *
     * @param cs the {@code CharSequence} to be processed
     * @param searchChar the {@code CharSequence} to be searched for
     * @param start the start index
     * @return the index where the search sequence was found
     */
    static int indexOf(final CharSequence cs, final CharSequence searchChar, final int start) {
        return cs.toString().indexOf(searchChar.toString(), start);
//        if (cs instanceof String && searchChar instanceof String) {
//            // TODO: Do we assume searchChar is usually relatively small;
//            //       If so then calling toString() on it is better than reverting to
//            //       the green implementation in the else block
//            return ((String) cs).indexOf((String) searchChar, start);
//        } else {
//            // TODO: Implement rather than convert to String
//            return cs.toString().indexOf(searchChar.toString(), start);
//        }
    }

    /**
     * <p>Finds the last index in the {@code CharSequence} that matches the
     * specified character.</p>
     *
     * @param cs  the {@code CharSequence} to be processed
     * @param searchChar  the char to be searched for
     * @param start  the start index, negative returns -1, beyond length starts at end
     * @return the index where the search char was found, -1 if not found
     */
    static int lastIndexOf(final CharSequence cs, final int searchChar, int start) {
        if (cs instanceof String) {
            return ((String) cs).lastIndexOf(searchChar, start);
        }
        final int sz = cs.length();
        if (start < 0) {
            return NOT_FOUND;
        }
        if (start >= sz) {
            start = sz - 1;
        }
        for (int i = start; i >= 0; --i) {
            if (cs.charAt(i) == searchChar) {
                return i;
            }
        }
        return NOT_FOUND;
    }

    /**
     * Used by the lastIndexOf(CharSequence methods) as a green implementation of lastIndexOf
     *
     * @param cs the {@code CharSequence} to be processed
     * @param searchChar the {@code CharSequence} to be searched for
     * @param start the start index
     * @return the index where the search sequence was found
     */
    static int lastIndexOf(final CharSequence cs, final CharSequence searchChar, final int start) {
        return cs.toString().lastIndexOf(searchChar.toString(), start);
//        if (cs instanceof String && searchChar instanceof String) {
//            // TODO: Do we assume searchChar is usually relatively small;
//            //       If so then calling toString() on it is better than reverting to
//            //       the green implementation in the else block
//            return ((String) cs).lastIndexOf((String) searchChar, start);
//        } else {
//            // TODO: Implement rather than convert to String
//            return cs.toString().lastIndexOf(searchChar.toString(), start);
//        }
    }

    /**
     * Green implementation of toCharArray.
     *
     * @param cs the {@code CharSequence} to be processed
     * @return the resulting char array
     */
    static char[] toCharArray(final CharSequence cs) {
        if (cs instanceof String) {
            return ((String) cs).toCharArray();
        }
        final int sz = cs.length();
        final char[] array = new char[cs.length()];
        for (int i = 0; i < sz; i++) {
            array[i] = cs.charAt(i);
        }
        return array;
    }

    /**
     * Green implementation of regionMatches.
     *
     * @param cs the {@code CharSequence} to be processed
     * @param ignoreCase whether or not to be case insensitive
     * @param thisStart the index to start on the {@code cs} CharSequence
     * @param substring the {@code CharSequence} to be looked for
     * @param start the index to start on the {@code substring} CharSequence
     * @param length character length of the region
     * @return whether the region matched
     */
    static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
            final CharSequence substring, final int start, final int length)    {
        if (cs instanceof String && substring instanceof String) {
            return ((String) cs).regionMatches(ignoreCase, thisStart, (String) substring, start, length);
        }
        int index1 = thisStart;
        int index2 = start;
        int tmpLen = length;

        // Extract these first so we detect NPEs the same as the java.lang.String version
        final int srcLen = cs.length() - thisStart;
        final int otherLen = substring.length() - start;

        // Check for invalid parameters
        if (thisStart < 0 || start < 0 || length < 0) {
            return false;
        }

        // Check that the regions are long enough
        if (srcLen < length || otherLen < length) {
            return false;
        }

        while (tmpLen-- > 0) {
            final char c1 = cs.charAt(index1++);
            final char c2 = substring.charAt(index2++);

            if (c1 == c2) {
                continue;
            }

            if (!ignoreCase) {
                return false;
            }

            // The same check as in String.regionMatches():
            if (Character.toUpperCase(c1) != Character.toUpperCase(c2)
                    && Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
                return false;
            }
        }

        return true;
    }
}

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