001 /*
002 * Copyright (C) 2012 eXo Platform SAS.
003 *
004 * This is free software; you can redistribute it and/or modify it
005 * under the terms of the GNU Lesser General Public License as
006 * published by the Free Software Foundation; either version 2.1 of
007 * the License, or (at your option) any later version.
008 *
009 * This software is distributed in the hope that it will be useful,
010 * but WITHOUT ANY WARRANTY; without even the implied warranty of
011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012 * Lesser General Public License for more details.
013 *
014 * You should have received a copy of the GNU Lesser General Public
015 * License along with this software; if not, write to the Free
016 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
017 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
018 */
019
020 package org.crsh.util;
021
022 /**
023 * An immutable sequence of white spaces.
024 */
025 public class BlankSequence implements CharSequence {
026
027 /** . */
028 private static final BlankSequence[] CACHE = new BlankSequence[64];
029
030 static {
031 for (int i = 0;i < CACHE.length;i++) {
032 CACHE[i] = new BlankSequence(i);
033 }
034 }
035
036 public static BlankSequence create(int length) {
037 if (length < 0) {
038 throw new IllegalArgumentException("No negative length accepted");
039 }
040 if (length < CACHE.length) {
041 return CACHE[length];
042 } else {
043 return new BlankSequence(length);
044 }
045 }
046
047 /** . */
048 private final int length;
049
050 /** . */
051 private String value;
052
053 /**
054 * Build a new blank sequence.
055 *
056 * @param length the length
057 * @throws IllegalArgumentException when length is negative
058 */
059 private BlankSequence(int length) throws IllegalArgumentException {
060 if (length < 0) {
061 throw new IllegalArgumentException();
062 }
063
064 //
065 this.length = length;
066 this.value = null;
067 }
068
069 public int length() {
070 return length;
071 }
072
073 public char charAt(int index) {
074 checkIndex("index", index);
075 return ' ';
076 }
077
078 public CharSequence subSequence(int start, int end) {
079 checkIndex("start", start);
080 checkIndex("end", end);
081 if (start > end) {
082 throw new IndexOutOfBoundsException("Start " + start + " cannot greater than end " + end);
083 }
084 return new BlankSequence(end - start);
085 }
086
087 @Override
088 public String toString() {
089 if (value == null) {
090 if (length == 0) {
091 value = "";
092 } else {
093 char[] chars = new char[length];
094 for (int i = 0;i < length;i++) {
095 chars[i] = ' ';
096 }
097 value = new String(chars, 0, chars.length);
098 }
099 }
100 return value;
101 }
102
103 private void checkIndex(String name, int index) {
104 if (index < 0) {
105 throw new IndexOutOfBoundsException("No negative " + name + " value " + index);
106 }
107 if (index >= length) {
108 throw new IndexOutOfBoundsException("The " + name + " value " + index + " cannot greater than length " + length);
109 }
110 }
111 }