channel代码示例

package cn.com.github.immortals;import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;import org.junit.Test;/** * * @author 潘琢文 * */
public class TestChannel {// 分散和聚集@Testpublic void test4() throws IOException {RandomAccessFile raf1 = new RandomAccessFile("1.txt", "rw");// 1. 获取通道FileChannel channel1 = raf1.getChannel();// 2. 分配指定大小的缓冲区ByteBuffer buf1 = ByteBuffer.allocate(100);ByteBuffer buf2 = ByteBuffer.allocate(1024);// 3. 分散读取ByteBuffer[] bufs = { buf1, buf2 };channel1.read(bufs);for (ByteBuffer byteBuffer : bufs) {byteBuffer.flip();}System.out.println(new String(bufs[0].array(), 0, bufs[0].limit()));System.out.println("-----------------");System.out.println(new String(bufs[1].array(), 0, bufs[1].limit()));// 4. 聚集写入RandomAccessFile raf2 = new RandomAccessFile("2.txt", "rw");FileChannel channel2 = raf2.getChannel();channel2.write(bufs);}/** * 利用channel复制文件 * * @throws IOException */@Testpublic void testChannel() throws IOException {FileInputStream ins = new FileInputStream(new File("D:/大话西游之大圣娶亲[国语版]_bd.mp4"));FileOutputStream fos = new FileOutputStream(new File("D:/大话西游之大圣娶亲[国语版]_bd_copy.mp4"));FileChannel in = ins.getChannel();FileChannel out = fos.getChannel();ByteBuffer buf = ByteBuffer.allocate(1024);while (in.read(buf) != -1) {buf.flip();out.write(buf);buf.clear();}ins.close();fos.close();in.close();out.close();}/** * channel的直接缓冲区复制文件 * * @throws IOException */@Testpublic void testChannel2() throws IOException {FileChannel in = FileChannel.open(Paths.get("D:/大话西游之大圣娶亲[国语版]_bd.mp4"), StandardOpenOption.READ);FileChannel out = FileChannel.open(Paths.get("D:/大话西游之大圣娶亲[国语版]_bd_copy.mp4"), StandardOpenOption.CREATE,StandardOpenOption.WRITE);in.transferTo(0, in.size(), out);in.close();out.close();}@Testpublic void testChannel3() throws IOException {FileChannel in = FileChannel.open(Paths.get("D:/大话西游之大圣娶亲[国语版]_bd.mp4"), StandardOpenOption.READ);FileChannel out = FileChannel.open(Paths.get("D:/大话西游之大圣娶亲[国语版]_bd_copy.mp4"), StandardOpenOption.CREATE,StandardOpenOption.WRITE, StandardOpenOption.READ);MappedByteBuffer inBuffer = in.map(MapMode.READ_ONLY, 0, in.size());MappedByteBuffer outBUffer = out.map(MapMode.READ_WRITE, 0, in.size());byte[] dst = new byte[inBuffer.limit()];inBuffer.get(dst);outBUffer.put(dst);in.close();out.close();}
}