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 }