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Java 为反向字符串创建CharSequence实现
为反向字符串创建CharSequence实现
实例源码：
源代码：
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// CharSequenceDemo presents a String value -- backwards.//n o w j a v a . c o m - 时 代 Java 提供3
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public class CharSequenceDemo implements CharSequence {5
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private String s;7
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public CharSequenceDemo(String s) {10
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//It would be much more efficient to just reverse the string12
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//in the constructor. But a lot less fun!14
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this.s = s;16
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}18
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//If the string is backwards, the end is the beginning!21
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private int fromEnd(int i) {23
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return s.length() - 1 - i;25
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}27
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public char charAt(int i) {30
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if ((i < 0) || (i >= s.length())) {32
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throw new StringIndexOutOfBoundsException(i);34
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}//时 代 J a v a 公 众 号 - nowjava.com 提供36
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return s.charAt(fromEnd(i));38
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}40
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public int length() {43
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return s.length();45
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}47
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public CharSequence subSequence(int start, int end) {50
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if (start < 0) {52
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throw new StringIndexOutOfBoundsException(start);54
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}56
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if (end > s.length()) {58
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throw new StringIndexOutOfBoundsException(end);60
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}62
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if (start > end) {64
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throw new StringIndexOutOfBoundsException(start - end);66
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}68
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StringBuilder sub = new StringBuilder(s.subSequence(fromEnd(end),70
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fromEnd(start)));72
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return sub.reverse();74
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}76
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public String toString() {79
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StringBuilder s = new StringBuilder(this.s);81
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return s.reverse().toString();83
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}85
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//Random int from 0 to max. As random() generates values between 0 and 0.999988
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private static int random(int max) {90
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return (int) Math.round(Math.random() * (max + 1));92
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}94
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public static void main(String[] args) {97
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CharSequenceDemo s = new CharSequenceDemo(99
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"Write a class that implements the CharSequence interface found in the java.lang package.");101
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//exercise charAt() and length()104
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for (int i = 0; i < s.length(); i++) {106
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System.out.print(s.charAt(i));108
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}110
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System.out.println("");113
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//exercise subSequence() and length();116
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int start = random(s.length() - 1);118
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int end = random(s.length() - 1 - start) + start;120
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System.out.println(s.subSequence(start, end));122
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//exercise toString();125
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System.out.println(s);127
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}130
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}132
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/*135
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* Copyright (c) 2008,2012 Oracle and/or its affiliates. All rights reserved.137
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*139
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* Redistribution and use in source and binary forms, with or without141
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* modification, are permitted provided that the following conditions143
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* are met:145
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*147
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* - Redistributions of source code must retain the above copyright149
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* notice, this list of conditions and the following disclaimer.151
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*153
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* - Redistributions in binary form must reproduce the above copyright155
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* notice, this list of conditions and the following disclaimer in the157
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* documentation and/or other materials provided with the distribution.159
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*161
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* - Neither the name of Oracle or the names of its163
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* contributors may be used to endorse or promote products derived165
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* from this software without specific prior written permission.167
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*169
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS171
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* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,173
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