java中文件复制的方式有哪些
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java中文件复制的4种方式
1. 使用FileStreams复制
比较经典的一个代码,使用FileInputStream读取文件A的字节,使用FileOutputStream写入到文件B。
public static void copy(String source, String dest, int bufferSize) { InputStream in = null; OutputStream out = null; try { in = new FileInputStream(new File(source)); out = new FileOutputStream(new File(dest)); byte[] buffer = new byte[bufferSize]; int len; while ((len = in.read(buffer)) > 0) { out.write(buffer, 0, len); } } catch (Exception e) { Log.w(TAG + ":copy", "error occur while copy", e); } finally { safelyClose(TAG + ":copy", in); safelyClose(TAG + ":copy", out); } } 2.
2、使用FileChannel
Java NIO包括transferFrom方法,根据文档应该比文件流复制的速度更快。
public static void copyNio(String source, String dest) { FileChannel input = null; FileChannel output = null; try { input = new FileInputStream(new File(from)).getChannel(); output = new FileOutputStream(new File(to)).getChannel(); output.transferFrom(input, 0, input.size()); } catch (Exception e) { Log.w(TAG + "copyNio", "error occur while copy", e); } finally { safelyClose(TAG + "copyNio", input); safelyClose(TAG + "copyNio", output); } } 3、 使用Apache Commons IO复制 Appache Commons IO 提供了一个FileUtils.copyFile(File from, File to)方法用于文件复制,如果项目里使用到了这个类库,使用这个方法是个不错的选择。 它的内部也是使用Java NIO的FileChannel实现的。 commons-io的路径:http://commons.apache.org/proper/commons-io/javadocs/api-release/index.html。里面还有很多实用的方法,如拷贝目录、拷贝指定格式文件等。
private static void copyFileByApacheCommonsIO(File source, File dest) throws IOException { FileUtils.copyFile(source, dest); }
4、使用Java7的Files类复制
private static void copyFileUsingJava7Files(File source, File dest) throws IOException { Files.copy(source.toPath(), dest.toPath()); }
我没有亲测,找了下网友的测试程序和输出,性能数据供大家参考
import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.nio.channels.FileChannel; import java.nio.file.Files; import org.apache.commons.io.FileUtils; public class CopyFilesExample { public static void main(String[] args) throws InterruptedException, IOException { File source = new File("C:\\Users\\nikos7\\Desktop\\files\\sourcefile1.txt"); File dest = new File("C:\\Users\\nikos7\\Desktop\\files\\destfile1.txt"); // copy file using FileStreams long start = System.nanoTime(); long end; copyFileUsingFileStreams(source, dest); System.out.println("Time taken by FileStreams Copy = " + (System.nanoTime() - start)); // copy files using java.nio.FileChannel source = new File("C:\\Users\\nikos7\\Desktop\\files\\sourcefile2.txt"); dest = new File("C:\\Users\\nikos7\\Desktop\\files\\destfile2.txt"); start = System.nanoTime(); copyFileUsingFileChannels(source, dest); end = System.nanoTime(); System.out.println("Time taken by FileChannels Copy = " + (end - start)); // copy file using Java 7 Files class source = new File("C:\\Users\\nikos7\\Desktop\\files\\sourcefile3.txt"); dest = new File("C:\\Users\\nikos7\\Desktop\\files\\destfile3.txt"); start = System.nanoTime(); copyFileUsingJava7Files(source, dest); end = System.nanoTime(); System.out.println("Time taken by Java7 Files Copy = " + (end - start)); // copy files using apache commons io source = new File("C:\\Users\\nikos7\\Desktop\\files\\sourcefile4.txt"); dest = new File("C:\\Users\\nikos7\\Desktop\\files\\destfile4.txt"); start = System.nanoTime(); copyFileUsingApacheCommonsIO(source, dest); end = System.nanoTime(); System.out.println("Time taken by Apache Commons IO Copy = " + (end - start)); } private static void copyFileUsingFileStreams(File source, File dest) throws IOException { InputStream input = null; OutputStream output = null; try { input = new FileInputStream(source); output = new FileOutputStream(dest); byte[] buf = new byte[1024]; int bytesRead; while ((bytesRead = input.read(buf)) > 0) { output.write(buf, 0, bytesRead); } } finally { input.close(); output.close(); } } private static void copyFileUsingFileChannels(File source, File dest) throws IOException { FileChannel inputChannel = null; FileChannel outputChannel = null; try { inputChannel = new FileInputStream(source).getChannel(); outputChannel = new FileOutputStream(dest).getChannel(); outputChannel.transferFrom(inputChannel, 0, inputChannel.size()); } finally { inputChannel.close(); outputChannel.close(); } } private static void copyFileUsingJava7Files(File source, File dest) throws IOException { Files.copy(source.toPath(), dest.toPath()); } private static void copyFileUsingApacheCommonsIO(File source, File dest) throws IOException { FileUtils.copyFile(source, dest); } }
输出:
Time taken by FileStreams Copy = 127572360
Time taken by FileChannels Copy = 10449963
Time taken by Java7 Files Copy = 10808333
Time taken by Apache Commons IO Copy = 17971677
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