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【第20章：Java新IO】_通道（Channel）

发布时间：2021-01-21 14:21:10编辑：雪饮阅读（）

 通道的输出流

import java.nio.ByteBuffer ;
import java.nio.channels.FileChannel ;
import java.io.File ;
import java.io.FileOutputStream ;
public class Hello{
       public static void main(String args[]) throws Exception {
              String info[] = {"kasumi,","ayane,","snowDrink,","momiji,","lisa,","momiji"} ;
              File file = new File("d:" + File.separator + "out.txt") ;
              FileOutputStream output = new FileOutputStream(file) ;
              FileChannel fout = output.getChannel() ;   // 得到输出的通道
              ByteBuffer buf = ByteBuffer.allocate(1024) ;
              for(int i=0;i<info.length;i++){
                     buf.put(info[i].getBytes()) ;   // 字符串变为字节数组放进缓冲区之中
              }
              buf.flip() ;
              fout.write(buf) ;     // 输出缓冲区的内容
              fout.close() ;
              output.close() ;
       }
};

输入、输出通道
import java.nio.ByteBuffer ;
import java.nio.channels.FileChannel ;
import java.io.File ;
import java.io.FileOutputStream ;
import java.io.FileInputStream ;
public class Hello{
       public static void main(String args[]) throws Exception {
              File file1 = new File("d:" + File.separator + "eula.2052.txt") ;
              File file2 = new File("d:" + File.separator + "outnote.txt") ;
              //第一个文件做为输入流
              FileInputStream input = new FileInputStream(file1) ;
              //第二个文件做为输出流
              FileOutputStream output = new FileOutputStream(file2) ;
              //输入通道
              FileChannel fin = input.getChannel();
              //输出通道
              FileChannel fout = output.getChannel();
             
              ByteBuffer buf = ByteBuffer.allocate(1024) ;
             
              int temp = 0 ;
              //每次读取完毕就重置下当前的buf的position和limit等，以免循环体的下一次执行时候以上一次的position个limit进行计算，那么后果不堪设想
              while((temp=fin.read(buf))!=-1){
                     buf.flip() ;
                     fout.write(buf) ;
                     // 清空缓冲区,所有的状态变量的位置恢复到原点
                     buf.clear() ;
              }
              fin.close() ;
              fout.close() ;
              input.close() ;
              output.close() ;
       }
};
D:\>javac Hello.java
D:\>java Hello
D:\>type outnote.txt
**You have received the software as part of the Visual Studio 9.0 Beta Program.
The terms and conditions of the Visual Studio 9.0, Beta 1 license agreement
applies to your use of the software.** MICROSOFT PRE-RELEASE SOFTWARE LICENSE
TERMS MICROSOFT VISUAL STUDIO 9.0 PROFESSIONAL, BETA 1 These license terms are
an agreement between Microsoft Corporation (or based on where you live, one of
its affiliates) and you. Please read them. They apply to the pre-release
software named above, which includes the media on which you received it, if any.
The terms also apply to any Microsoft • updates, • supplements, • Internet-based
services, and • support services for this software, unless other terms accompany
those items. If so, those terms apply. BY USING THE SOFTWARE, YOU ACCEPT THESE
TERMS. IF YOU DO NOT ACCEPT THEM, DO NOT USE THE SOFTWARE. If you comply with
these license terms, you have the rights below. 1. INSTALLATION AND USE RIGHTS.
• General. You may install and use one copy of the software on your premises to
design, develop and test your programs for use with the software. • Evaluation
Only. The software is for evaluation purposes only. You may not distribute any
program you develop with the software. • Included Microsoft Programs. These
license terms apply to all Microsoft programs included with the software. •
Third Party Programs. The software contains third party programs. The license
terms with those programs apply to your use of them. 2. INTERNET-BASED SERVICES.
Microsoft provides Internet-based services with the software. It may change or
cancel them at any time. 3. TIME-SENSITIVE SOFTWARE. The software will stop
running on 15 March 2008. You will not receive any other notice. You may not be
able to access data used with the software when it stops running. 4. PRE-RELEASE
SOFTWARE. This software is a pre-release version. It may not work the way a
final version of the software will. We may change it for the final, commercial
version. We also may not release a commercial version. 5. FEEDBACK. If you give
feedback about the software to Microsoft, you give to Microsoft, without charge,
the right to use, share and commercialize your feedback in any way and for any
purpose. You also give to third parties, without charge, any patent rights
needed for their products, technologies and services to use or interface with
any specific parts of a Microsoft software or service that includes the
feedback. You will not give feedback that is subject to a license that requires
Microsoft to license its software or documentation to third parties because we
include your feedback in them. These rights survive this agreement. 6. SCOPE OF
LICENSE. The software is licensed, not sold. This agreement only gives you some
rights to use the software. Microsoft reserves all other rights. Unless
applicable law gives you more rights despite this limitation, you may use the
software only as expressly permitted in this agreement. In doing so, you must
comply with any technical limitations in the software that only allow you to use
it in certain ways. You may not • disclose the results of any benchmark tests of
the software to any third party without Microsoft’s prior written approval; •
work around any technical limitations in the software; • reverse engineer,
decompile or disassemble the software, except and only to the extent that
applicable law expressly permits, despite this limitation; • make more copies of
the software than specified in this agreement or allowed by applicable law,
despite this limitation; • publish the software for others to copy; • rent,
lease or lend the software; • transfer the software or this agreement to any
third party; or • use the software for commercial software hosting services. 7.
EXPORT RESTRICTIONS. The software is subject to United States export laws and
regulations. You must comply with all domestic and international export laws and
regulations that apply to the software. These laws include restrictions on
destinations, end users and end use. For additional information, see
www.microsoft.com/exporting. 8. SUPPORT SERVICES. Because this software is “as
is,” we may not provide support services for it. 9. ENTIRE AGREEMENT. This
agreement, and the terms for supplements, updates, Internet-based services and
support services that you use, are the entire agreement for the software and
support services. 10. APPLICABLE LAW. a. United States. If you acquired the
software in the United States, Washington state law governs the interpretation
of this agreement and applies to claims for breach of it, regardless of conflict
of laws principles. The laws of the state where you live govern all other
claims, including claims under state consumer protection laws, unfair
competition laws, and in tort. b. Outside the United States. If you acquired the
software in any other country, the laws of that country apply. 11. LEGAL EFFECT.
This agreement describes certain legal rights. You may have other rights under
the laws of your country. You may also have rights with respect to the party
from whom you acquired the software. This agreement does not change your rights
under the laws of your country if the laws of your country do not permit it to
do so. 12. DISCLAIMER OF WARRANTY. THE SOFTWARE IS LICENSED “AS-IS.” YOU BEAR
THE RISK OF USING IT. MICROSOFT GIVES NO EXPRESS WARRANTIES, GUARANTEES OR
CONDITIONS. YOU MAY HAVE ADDITIONAL CONSUMER RIGHTS UNDER YOUR LOCAL LAWS WHICH
THIS AGREEMENT CANNOT CHANGE. TO THE EXTENT PERMITTED UNDER YOUR LOCAL LAWS,
MICROSOFT EXCLUDES THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NON-INFRINGEMENT. 13. LIMITATION ON AND EXCLUSION OF
REMEDIES AND DAMAGES. YOU CAN RECOVER FROM MICROSOFT AND ITS SUPPLIERS ONLY
DIRECT DAMAGES UP TO U.S. $5.00. YOU CANNOT RECOVER ANY OTHER DAMAGES, INCLUDING
CONSEQUENTIAL, LOST PROFITS, SPECIAL, INDIRECT OR INCIDENTAL DAMAGES. This
limitation applies to • anything related to the software, services, content
(including code) on third party Internet sites, or third party programs; and •
claims for breach of contract, breach of warranty, guarantee or condition,
strict liability, negligence, or other tort to the extent permitted by
applicable law. It also applies even if Microsoft knew or should have known
about the possibility of the damages. The above limitation or exclusion may not
apply to you because your country may not allow the exclusion or limitation of
incidental, consequential or other damages. Please note: As this software is
distributed in Quebec, Canada, some of the clauses in this agreement are
provided below in French. Remarque : Ce logiciel étant distribué au Québec,
Canada, certaines des clauses dans ce contrat sont fournies ci-dessous en
français. EXONÉRATION DE GARANTIE. Le logiciel visé par une licence est offert «
tel quel ». Toute utilisation de ce logiciel est à votre seule risque et péril.
Microsoft n’accorde aucune autre garantie expresse. Vous pouvez bénéficier de
droits additionnels en vertu du droit local sur la protection des consommateurs,
que ce contrat ne peut modifier. La ou elles sont permises par le droit locale,
les garanties implicites de qualité marchande, d’adéquation à un usage
particulier et d’absence de contrefaçon sont exclues. LIMITATION DES
DOMMAGES-INTÉRÊTS ET EXCLUSION DE RESPONSABILITÉ POUR LES DOMMAGES. Vous pouvez
obtenir de Microsoft et de ses fournisseurs une indemnisation en cas de dommages
directs uniquement à hauteur de 5,00 $ US. Vous ne pouvez prétendre à aucune
indemnisation pour les autres dommages, y compris les dommages spéciaux,
indirects ou accessoires et pertes de bénéfices. Cette limitation concerne : •
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n’autorise pas l’exclusion ou la limitation de responsabilité pour les dommages
indirects, accessoires ou de quelque nature que ce soit, il se peut que la
limitation ou l’exclusion ci-dessus ne s’appliquera pas à votre égard. EFFET
JURIDIQUE. Le présent contrat décrit certains droits juridiques. Vous pourriez
avoir d’autres droits prévus par les lois de votre pays. Le présent contrat ne
modifie pas les droits que vous confèrent les lois de votre pays si celles-ci ne
le permettent pas.
通道与内存映射
import java.nio.ByteBuffer ;
import java.nio.MappedByteBuffer ;
import java.nio.channels.FileChannel ;
import java.io.File ;
import java.io.FileOutputStream ;
import java.io.FileInputStream ;
public class Hello{
       public static void main(String args[]) throws Exception {
              //输入通道
              File file = new File("d:" + File.separator + "outnote.txt") ; 
              FileInputStream input = new FileInputStream(file);
              FileChannel fin = input.getChannel();
              //以只读模式建立输入通道与内存的映射关系
              MappedByteBuffer mbb = fin.map(FileChannel.MapMode.READ_ONLY,0,file.length()) ;
             
              byte data[] = new byte[(int)file.length()] ;   // 开辟空间接收内容
              int foot = 0 ;
              while(mbb.hasRemaining()){
                     data[foot++] = mbb.get() ; // 读取数据
              }
              System.out.println(new String(data)) ; // 输出内容
              fin.close() ;
              input.close() ;
       }
};
D:\>javac Hello.java
D:\>java Hello
?m o d i f i e   p a s   l e s   d r o i t s   q u e   v o u s   c o n f ?r e n t   l e s   l o i s   d e   v o t r e     a y s   s i   c e l l e s - c i   n e
 l e   p e r m e t t e n t   p a s .