java 文件复制测试

最新推荐文章于 2025-01-12 19:12:26 发布

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本文通过代码对比了内存文件映像、旧的IO方式、管道与管道方式及使用直接缓存四种复制大文件的方法，并给出了每种方法的耗时结果。

闲来无聊，对比下新旧IO复制文件的性能，贴代码了：


import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;

import org.junit.Test;

public class FileCopyTest{

	private File f1 = new File("d:\\temp\\bigfile.rar");//2.8G

	@Test
	/**
	 * 内存文件映像方式
	 */
	public void testMappedByteBuffer() throws Exception {
		long time = System.currentTimeMillis();
		File f2 =  new File("d:\\temp\\1.rar");
		if (f2.exists()) {
			f2.delete();
		} else {
			f2.createNewFile();
		}

		FileInputStream fin = new FileInputStream(f1);
		FileOutputStream fos = new FileOutputStream(f2);

		FileChannel finc = fin.getChannel();
		FileChannel fosc = fos.getChannel();

		long length = f1.length();
		long size = 1024*1024*10;//10M
		long position = 0;
		MappedByteBuffer mbb =  null;
		while(position<length){
			long readLength = size;
			if(position+size>length){
				readLength = length - position;
			}
			mbb = finc.map(MapMode.READ_ONLY, position, readLength);
			fosc.write(mbb);
			fosc.force(true);//强制读取数据磁盘写操作
			mbb.clear();
			position += readLength;
		}

		fosc.close();
		finc.close();
		fos.close();
		fin.close();

		time = System.currentTimeMillis() - time;
		System.out.println("MappedByteBuffer cost time(ms)=" + time);
	}

	@Test
	/**
	 * 旧的IO方式
	 */
	public void testOldIO() throws Exception {
		long time = System.currentTimeMillis();
		File f2 = new File("d:\\temp\\2.rar");
		if (f2.exists()) {
			f2.delete();
		} else {
			f2.createNewFile();
		}

		FileInputStream fin = new FileInputStream(f1);
		FileOutputStream fos = new FileOutputStream(f2);

		byte[] b = new byte[1024 * 1024*10];
        int count=-1;
		while ((count = fin.read(b)) != -1) {
			fos.write(b,0,count);
		}
		fos.close();
		fin.close();

		time = System.currentTimeMillis() - time;
		System.out.println("old I/O cost time(ms)=" + time);
	}

	@Test
	/**
	 * 管道与管道方式
	 */
	public void testTransfer() throws Exception {
		long time = System.currentTimeMillis();
		File f2 =  new File("d:\\temp\\3.rar");
		if (f2.exists()) {
			f2.delete();
		} else {
			f2.createNewFile();
		}

		FileInputStream fin = new FileInputStream(f1);
		FileOutputStream fos = new FileOutputStream(f2);

		FileChannel finc = fin.getChannel();
		FileChannel fosc = fos.getChannel();

		long length = f1.length();
		long size = 1024*1024*10;//10M
		long position = 0;
		while(position<length){
			long readLength = size;
			if(position+size>length){
				readLength = length - position;
			}
			finc.transferTo(position, readLength, fosc);
			fosc.force(true);//强制读取数据磁盘写操作
			position += readLength;
		}

		fosc.close();
		finc.close();

		fos.close();
		fin.close();

		time = System.currentTimeMillis() - time;
		System.out.println("Transfer cost time(ms)=" + time);
	}

	@Test
	/**
	 * 管道与管道方式（使用直接缓存）
	 */
	public void testChannel() throws Exception{
        long time= System.currentTimeMillis();
        File f2 =  new File("d:\\temp\\4.rar");
		if (f2.exists()) {
			f2.delete();
		} else {
			f2.createNewFile();
		}

		FileInputStream fin = new FileInputStream(f1);
		FileOutputStream fos = new FileOutputStream(f2);

		FileChannel finc = fin.getChannel();
		FileChannel fosc = fos.getChannel();

        ByteBuffer b= ByteBuffer.allocateDirect(1024*1024*10);
        while(finc.read(b)!=-1){
            b.flip();
            fosc.write(b);
            fosc.force(false);
            b.clear();
        }

        fosc.close();
		finc.close();

		fos.close();
		fin.close();

		time = System.currentTimeMillis() - time;
		System.out.println("Channel cost time(ms)=" + time);
    }
}