Java tutorial
/* * 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 * @version $Id$ */ 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; 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; } }