Java 实现CharSequence以创建类似类的字符串
实现CharSequence以创建类似类的字符串
实例源码：
源代码：
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// CharSequenceDemo presents a String value -- backwards.3
/**4
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* N o w J a v a . c o m 6
**/7
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public class CharSequenceDemo implements CharSequence {9
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private String s;11
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public CharSequenceDemo(String s) {14
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//It would be much more efficient to just reverse the string16
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//in the constructor. But a lot less fun!18
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this.s = s;20
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}22
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//If the string is backwards, the end is the beginning!25
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private int fromEnd(int i) {27
/* 28
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*时 代 J a v a 公 众 号 - nowjava.com*/30
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return s.length() - 1 - i;32
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}34
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public char charAt(int i) {37
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if ((i < 0) || (i >= s.length())) {39
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throw new StringIndexOutOfBoundsException(i);41
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}43
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return s.charAt(fromEnd(i));45
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}47
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public int length() {50
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return s.length();52
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}54
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public CharSequence subSequence(int start, int end) {57
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if (start < 0) {59
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throw new StringIndexOutOfBoundsException(start);61
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}63
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if (end > s.length()) {65
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throw new StringIndexOutOfBoundsException(end);67
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}69
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if (start > end) {71
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throw new StringIndexOutOfBoundsException(start - end);73
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}75
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StringBuilder sub = new StringBuilder(s.subSequence(fromEnd(end),77
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fromEnd(start)));79
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return sub.reverse();81
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}83
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public String toString() {86
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StringBuilder s = new StringBuilder(this.s);88
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return s.reverse().toString();90
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}92
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//Random int from 0 to max.95
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private static int random(int max) {97
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return (int) Math.round(Math.random() * max + 0.5);99
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}101
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public static void main(String[] args) {104
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CharSequenceDemo s = new CharSequenceDemo(106
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"Write a class that implements the CharSequence interface found in the java.lang package.");108
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//exercise charAt() and length()111
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for (int i = 0; i < s.length(); i++) {113
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System.out.println(s.charAt(i));115
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}117
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//exercise subSequence() and length();120
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int start = random(s.length() - 1);122
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int end = random(s.length() - 1 - start) + start;124
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System.out.println(s.subSequence(start, end));126
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//exercise toString();129
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System.out.println(s);131
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}134
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}136
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/*139
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* Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.141
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*143
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* Redistribution and use in source and binary forms, with or without145
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* modification, are permitted provided that the following conditions147
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* are met:149
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*151
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* - Redistributions of source code must retain the above copyright153
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* notice, this list of conditions and the following disclaimer.155
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*157
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* - Redistributions in binary form must reproduce the above copyright159
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* notice, this list of conditions and the following disclaimer in the161
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* documentation and/or other materials provided with the distribution.163
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*165
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* - Neither the name of Oracle or the names of its167
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* contributors may be used to endorse or promote products derived169
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* from this software without specific prior written permission.171
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*173
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS175
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* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,177
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