java 文件复制

使用FileInputStream+BufferedInputStream与FileOutputStream+BufferedOutputStream实现文件复制，是很多人普遍想到的一种方法。在这里，我将给出另外一种方法，使用FileChannel通道。其实，还有一些其他方法，想了解更多，清参见我转载的文章：JAVA NIO 简介。

不多说，直接贴出源码：

srcFile和destFile：均为文件而非目录；

overlay：指示是否覆盖已存在目标文件。

 

package com.pluto.file;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

public class FileCopy {
	private final int BUFFER_SIZE = 4096;

	public long bufferCopyFile(File srcFile, File destFile, boolean overlay) throws FileNotFoundException {
		if (!srcFile.exists()) {
			throw new FileNotFoundException("At path " + srcFile.getAbsolutePath());
		}

		if (destFile.exists() && overlay) {
			destFile.delete();
		}

		BufferedInputStream bufin = new BufferedInputStream(new FileInputStream(srcFile));
		BufferedOutputStream bufout = new BufferedOutputStream(new FileOutputStream(destFile));
		byte[] buffer = new byte[BUFFER_SIZE];
		long totalBytesReaded = 0;
		int bytesReaded = -1;
		try {
			while ((bytesReaded = bufin.read(buffer, 0, BUFFER_SIZE)) != -1) {
				bufout.write(buffer, 0, bytesReaded);
				totalBytesReaded += bytesReaded;
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				bufin.close();
				bufout.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}

		return totalBytesReaded;
	}

	public long channelCopyFile(File srcFile, File destFile, boolean overlay) throws FileNotFoundException {
		if (!srcFile.exists()) {
			throw new FileNotFoundException("At path " + srcFile.getAbsolutePath());
		}

		if (destFile.exists() && overlay) {
			destFile.delete();
		}

		// 获取源文件和目标文件的输入输出流
		FileInputStream fin = new FileInputStream(srcFile);
		FileOutputStream fout = new FileOutputStream(destFile);
		// 获取输入输出通道
		FileChannel fcin = fin.getChannel();
		FileChannel fcout = fout.getChannel();
		long totalBytesReaded = 0;
		try{
			totalBytesReaded = fcin.transferTo(0, fcin.size(), fcout);
		}catch(IOException e){
			e.printStackTrace();
		} finally {
			try {
				fin.close();
				fout.close();
				fcin.close();
				fcout.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		
		return totalBytesReaded;
	}
}

 

 

在本机上面做了个简单的性能测试。在下面的测试源码中，beautiful.rmvb是一个600M左右的文件

 

 

		FileCopy fileCopy = new FileCopy();
		File srcFile = new File("/home/pluto/temporary/filecopy/beautiful.rmvb");
		File destFile1 = new File("/home/pluto/temporary/filecopy/dest/b.rmvb");
		File destFile2 = new File("/home/pluto/temporary/filecopy/dest/be.rmvb");
		long totalBytes = 0;
		long start = System.currentTimeMillis();
		try {
			totalBytes = fileCopy.bufferCopyFile(srcFile, destFile1, false);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
		long end = System.currentTimeMillis();
		System.out.println("bufferCopyFile: " + totalBytes + "  spend: " + (end - start));
		
		start = System.currentTimeMillis();
		try {
			totalBytes = fileCopy.channelCopyFile(srcFile, destFile2, false);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
		end = System.currentTimeMillis();
		System.out.println("\nchannelCopyFile: " + totalBytes + "  spend: " + (end - start));

 

运行输出结果如下：

 

 

bufferCopyFile: 685049654  spend: 26077

channelCopyFile: 685049654  spend: 28345

 我的电脑性能一般，上面的结果只具有参考性。