filechannel

Disadvantage of FileChannel -> BufferedReader -> Reader

由 余生颓废 提交于 2020-04-10 06:05:45
问题 FileChannel will faster than BufferedReader , BufferedReader will more faster than Reader because FileChannel and BufferedReader has cut off some itermediate steps to receive data. My question is : the advantage is obvious, but I don't see any source on web say about its disadvantage. (of FileChannel to BufferedReader , BufferedReader to Reader ). What a problem when we cut off intermediate steps between. So, who can teach me,please. @:And, the same question for Output, too. Please tell me

Disadvantage of FileChannel -> BufferedReader -> Reader

由 懵懂的女人 提交于 2020-04-10 06:03:55
问题 FileChannel will faster than BufferedReader , BufferedReader will more faster than Reader because FileChannel and BufferedReader has cut off some itermediate steps to receive data. My question is : the advantage is obvious, but I don't see any source on web say about its disadvantage. (of FileChannel to BufferedReader , BufferedReader to Reader ). What a problem when we cut off intermediate steps between. So, who can teach me,please. @:And, the same question for Output, too. Please tell me

Java NIO基础知识整理（一）

由 社会主义新天地 提交于 2020-03-01 00:28:18
NIO 特性 1、 为原始类提供缓存支持； 2 、字符集编码解码解决方案； 3 、 Channel ：一个新的原始 I/O 抽象； 4 、支持锁和内存映射文件的文件访问接口； 5 、提供多路非阻塞式（ non-bloking ）的高伸缩性网络 I/O 。 Buffer 在基本 I/O 操作中所有的操作都是直接以流的形式完成的，而在 NIO 中所有的操作都要使用到缓冲区处理，且所有的读写操作都是通过缓冲区完成的。缓冲区（ Buffer ）是一个线性的、有序的数据集，只能容纳某种特定的数据类型。 一个 Buffer 有以下几个属性： 容量（ capacity ） ：缓冲区能包含的元素的最大数目。 限制（ limit ） ：第一个无法被写入或读取的元素坐标。 坐标（ position ） ：下一个要写入或读取的元素的坐标。 更多 Buffer 的属性和方法参考 http://download.oracle.com/javase/6/docs/api/ 。 另外， http://www.linuxtopia.org/online_books/programming_books/thinking_in_java/TIJ314_027.htm 上面有一个各种类型的 Buffer 和 byte[] 之间相互转换的模型图，挺有帮助的。 图 1 Buffer 内部结构 看一下一个简单的示例

Is FileChannel#force is equivalent to OutputStream#flush? Do I always have to call it?

由 人盡茶涼 提交于 2020-01-06 19:26:17
问题 I have a class works like FilterOutputStream . public class WritableFilterChannel implements WritableChannel { public WritableFilterChannel(final WritableByteChannel channel) { super(); this.channel = channel; } // isOpen(), close() delegates to the channel // write(ByteBuffer) overridden to work differently protected WritableByteChannel channel; } When I pass an instance of FileChannel , there is no way to force() other than close() it. Is FileChannel#force is equivalent to OutputStream

MappedByteBuffer slow on initial run

由 岁酱吖の 提交于 2020-01-06 12:49:07
问题 long time reader, first time poster. I'm having a bit of trouble reading data quickly from a set of binary files. ByteBuffers and MappedBytBuffers offer the performance I require but they seem to require an initial run to warm up. I'm not sure if that makes sense so here's some code: int BUFFERSIZE = 864; int DATASIZE = 33663168; int pos = 0; // Open File channel to get data FileChannel channel = new RandomAccessFile(new File(myFile), "r").getChannel(); // Set MappedByteBuffer to read

MappedByteBuffer slow on initial run

由 一曲冷凌霜 提交于 2020-01-06 12:48:50
问题 long time reader, first time poster. I'm having a bit of trouble reading data quickly from a set of binary files. ByteBuffers and MappedBytBuffers offer the performance I require but they seem to require an initial run to warm up. I'm not sure if that makes sense so here's some code: int BUFFERSIZE = 864; int DATASIZE = 33663168; int pos = 0; // Open File channel to get data FileChannel channel = new RandomAccessFile(new File(myFile), "r").getChannel(); // Set MappedByteBuffer to read

Using FileChannel to write any InputStream?

由 和自甴很熟 提交于 2019-12-30 04:15:39
问题 Can I write any InputStream into a FileChannel? I'm using java.nio.channels.FileChannel to open a file and lock it, then writing a InputStream to the output file. The InputStream may be opened by another file, URL, socket, or anything. I've write the following codes: FileOutputStream outputStream = new FileOutputStream(outputFile); FileChannel outputChannel = outputStream.getChannel(); FileLock lock = outputChannel.lock(); try { outputChannel.transferFrom(???); } finally { lock.release();

FileChannel.transferFrom fails for larger files with Out of memory Error

由 喜你入骨 提交于 2019-12-23 22:16:13
问题 FileChannel.transferFrom(source, 0, source.size()) gives the following OutOfMemory exception, when trying to copy a file of size around 2GB. I understand the memory issue due to larger files. Can we solve it by coping the file in small chunks, in a loop? 01-22 17:27:03.365: W/System.err(28538): java.io.IOException: mmap failed: ENOMEM (Out of memory) 01-22 17:27:03.375: W/System.err(28538): at java.nio.MemoryBlock.mmap(MemoryBlock.java:119) 01-22 17:27:03.375: W/System.err(28538): at java.nio

Reading an ASCII file with FileChannel and ByteArrays

由 我只是一个虾纸丫 提交于 2019-12-22 06:17:11
问题 I have the following code: String inputFile = "somefile.txt"; FileInputStream in = new FileInputStream(inputFile); FileChannel ch = in.getChannel(); ByteBuffer buf = ByteBuffer.allocateDirect(BUFSIZE); // BUFSIZE = 256 /* read the file into a buffer, 256 bytes at a time */ int rd; while ( (rd = ch.read( buf )) != -1 ) { buf.rewind(); for ( int i = 0; i < rd/2; i++ ) { /* print each character */ System.out.print(buf.getChar()); } buf.clear(); } But the characters get displayed at ?'s. Does

Reading an ASCII file with FileChannel and ByteArrays

由 别说谁变了你拦得住时间么 提交于 2019-12-22 06:17:10
问题 I have the following code: String inputFile = "somefile.txt"; FileInputStream in = new FileInputStream(inputFile); FileChannel ch = in.getChannel(); ByteBuffer buf = ByteBuffer.allocateDirect(BUFSIZE); // BUFSIZE = 256 /* read the file into a buffer, 256 bytes at a time */ int rd; while ( (rd = ch.read( buf )) != -1 ) { buf.rewind(); for ( int i = 0; i < rd/2; i++ ) { /* print each character */ System.out.print(buf.getChar()); } buf.clear(); } But the characters get displayed at ?'s. Does
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