java中怎么实现文件拷贝功能
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1. 通过字节流实现文件的拷贝
/** * 通过字节流实现文件的拷贝 * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByStream(String sourcePath,String targetPath){ //源文件路径 File source = new File(sourcePath); //目标文件路径 File target = new File(targetPath); //如果源文件不存在则不能拷贝 if(!source.exists()){ return; } //如果目标文件目录不存在则创建 if(!target.getParentFile().exists()){ target.getParentFile().mkdirs(); } try { //实现文件的拷贝 InputStream inputStream = new FileInputStream(source); OutputStream outputStream = new FileOutputStream(target); int temp = 0; //每次读取1024个字节 byte[] data = new byte[1024]; //将每次读取的数据保存到字节数组里面，并且返回读取的个数 while ((temp = inputStream.read(data)) != -1){ //输出数组 outputStream.write(data,0,temp); } inputStream.close(); outputStream.close(); } catch (IOException e) { e.printStackTrace(); } }
2. 通过字符流实现文件拷贝
使用字符流只能拷贝文本文件
/** * 通过字符流实现文件的拷贝 * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByReaderAndWriter(String sourcePath, String targetPath) { //源文件路径 File source = new File(sourcePath); //目标文件路径 File target = new File(targetPath); //如果源文件不存在则不能拷贝 if (!source.exists()) { return; } //如果目标文件目录不存在则创建 if (!target.getParentFile().exists()) { target.getParentFile().mkdirs(); } FileReader in = null; FileWriter out = null; try { //字符输入流和字符输出流 in = new FileReader(source); out = new FileWriter(target); char[] c = new char[1024]; int temp = 0; //每次读取1024个字符 while ((temp = in.read(c)) != -1) { //输出到文件 out.write(c, 0, temp); } } catch (IOException e) { e.printStackTrace(); } finally { //关闭流 try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException e) { e.printStackTrace(); } } }
3. 通过字节缓冲流实现文件拷贝
/** * 通过字节缓冲流实现文件的拷贝 * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByBuffered(String sourcePath, String targetPath){ //源文件路径 File source = new File(sourcePath); //目标文件路径 File target = new File(targetPath); //如果源文件不存在则不能拷贝 if (!source.exists()) { return; } //如果目标文件目录不存在则创建 if (!target.getParentFile().exists()) { target.getParentFile().mkdirs(); } InputStream in = null; OutputStream out = null; try { //字节缓冲输入流和字节缓冲输出流 in = new BufferedInputStream(new FileInputStream(source)); out = new BufferedOutputStream(new FileOutputStream(target)); byte[] b = new byte[1024]; int temp = 0; //每次读取一个1024的字节数组 while((temp = in.read(b)) != -1){ //输出到文件 out.write(b,0,temp); } } catch (Exception e) { e.printStackTrace(); }finally { //关闭流 try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException e) { e.printStackTrace(); } } }
4. 通过字符缓冲流拷贝文件
字符缓冲流只能读取文本文件
/** * 通过字符缓冲流实现文件的拷贝 * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByBufferedChar(String sourcePath, String targetPath){ //源文件路径 File source = new File(sourcePath); //目标文件路径 File target = new File(targetPath); //如果源文件不存在则不能拷贝 if (!source.exists()) { return; } //如果目标文件目录不存在则创建 if (!target.getParentFile().exists()) { target.getParentFile().mkdirs(); } BufferedReader in = null; BufferedWriter out = null; try { //字符缓冲输入流和字符缓冲输出流 in = new BufferedReader(new FileReader(source)); out = new BufferedWriter(new FileWriter(target)); //读取文件（每次读取一行） String temp = null; while((temp = in.readLine()) != null){ //输出到文件 out.write(temp); } } catch (Exception e) { e.printStackTrace(); }finally { //关闭流 try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException e) { e.printStackTrace(); } } }
5. 通过JAVA NIO 非直接缓冲区拷贝文件
/** * 通过JAVA NIO 非直接缓冲区拷贝文件 * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByChannel(String sourcePath, String targetPath) { FileChannel outChannel = null; FileChannel inChannel = null; FileInputStream fis = null; FileOutputStream fos = null; try { fis = new FileInputStream(sourcePath); fos = new FileOutputStream(targetPath); //获取通道 inChannel = fis.getChannel(); outChannel = fos.getChannel(); //分配指定大小的缓冲区 ByteBuffer buf = ByteBuffer.allocate(1024); while (inChannel.read(buf) != -1) { //转换为读取数据模式 buf.flip(); //写入到磁盘 outChannel.write(buf); //清空缓冲区 buf.clear(); } } catch (Exception e) { e.printStackTrace(); } finally { //关闭流 try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } if (fis != null) { fis.close(); } if (fos != null) { fos.close(); } } catch (IOException e) { e.printStackTrace(); } } }
6. 通过JAVA NIO 直接缓冲区拷贝文件
/** * 通过JAVA NIO 直接缓冲区拷贝文件（内存映射文件） * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByChannelBufferd(String sourcePath, String targetPath) { FileChannel inChannel = null; FileChannel outChannel = null; try { //获取通道,StandardOpenOption.READ表示可读，StandardOpenOption.WRITE表示可写，StandardOpenOption.CREATE表示可以创建 inChannel = FileChannel.open(Paths.get(sourcePath), StandardOpenOption.READ); outChannel = FileChannel.open(Paths.get(targetPath), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE); //创建内存映射文件 MappedByteBuffer inMapped = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size()); MappedByteBuffer outMapped = outChannel.map(FileChannel.MapMode.READ_WRITE, 0, inChannel.size()); //直接操作内存映射文件 byte[] buf = new byte[inMapped.limit()]; inMapped.get(buf); outMapped.put(buf); } catch (IOException e) { e.printStackTrace(); } finally { //关闭流 try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } } catch (IOException e) { e.printStackTrace(); } } }
7. 通过JAVA NIO 通道传输拷贝文件
方式一
/** * 通过JAVA NIO 通道传输拷贝文件 * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByChannelTransfer(String sourcePath, String targetPath) { FileChannel inChannel = null; FileChannel outChannel = null; try { //获取通道 inChannel = FileChannel.open(Paths.get(sourcePath), StandardOpenOption.READ); outChannel = FileChannel.open(Paths.get(targetPath),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE); inChannel.transferTo(0,inChannel.size(),outChannel); } catch (IOException e) { e.printStackTrace(); }finally { //关闭流 try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } } catch (IOException e) { e.printStackTrace(); } } }
方式二
/** * 通过JAVA NIO 通道传输拷贝文件 * * @param sourcePath 源文件路径 * @param targetPath 目标文件路径 */ public static void copyFileByChannelTransfer2(String sourcePath, String targetPath) { FileInputStream fis = null; FileOutputStream fos = null; FileChannel inChannel = null; FileChannel outChannel = null; try { fis = new FileInputStream(sourcePath); fos = new FileOutputStream(targetPath); //获取通道 inChannel = fis.getChannel(); outChannel = fos.getChannel(); inChannel.transferTo(0,inChannel.size(),outChannel); } catch (IOException e) { e.printStackTrace(); }finally { //关闭流 try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } } catch (IOException e) { e.printStackTrace(); } } }
使用示例
String source = "e:\\demo\\纵天神帝.txt"; String target = "e:\\demo\\"; long time1 = System.currentTimeMillis(); copyFileByStream(source, target + "1.txt"); System.out.println("通过字节流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time1)); long time2 = System.currentTimeMillis(); copyFileByReaderAndWriter(source, target + "2.txt"); System.out.println("通过字符流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time2)); long time3 = System.currentTimeMillis(); copyFileByBuffered(source, target + "3.txt"); System.out.println("通过字节缓冲流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time3)); long time4 = System.currentTimeMillis(); copyFileByBufferedChar(source, target + "4.txt"); System.out.println("通过字符缓冲流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time4)); long time5 = System.currentTimeMillis(); copyFileByChannel(source, target + "5.txt"); System.out.println("通过JAVA NIO通道（非直接缓冲区）实现文件的拷贝耗时：" + (System.currentTimeMillis() - time5)); long time6 = System.currentTimeMillis(); copyFileByChannelBufferd(source, target + "6.txt"); System.out.println("通过JAVA NIO通道（直接缓冲区）实现文件的拷贝耗时：" + (System.currentTimeMillis() - time6)); long time7 = System.currentTimeMillis(); copyFileByChannelTransfer(source, target + "7.txt"); System.out.println("通过JAVA NIO通道传输实现文件的拷贝耗时：" + (System.currentTimeMillis() - time7)); long time8 = System.currentTimeMillis(); copyFileByChannelTransfer(source, target + "8.txt"); System.out.println("通过JAVA NIO通道传输2实现文件的拷贝耗时：" + (System.currentTimeMillis() - time8));
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