作业四

一、源程序
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class CopyFile {

/**
 * @param args
 */
public static void copy(File a,File b){
	try {
		FileInputStream fis = new FileInputStream("a.mp3");
		FileOutputStream fos = new FileOutputStream("temp.mp3");
		byte[] buf = new byte[2048];
		int length;
		int read = fis.read();
		while((length = fis.read(buf))!=-1){
			fos.write(buf, 0, length);
		}
		fis.close();
		fos.close();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
}
public static void main(String[] args) {
	// TODO Auto-generated method stub
	File a = new File("");
	File b = new File("");
	long start,end;
	start = System.currentTimeMillis();
	copy(a,b);
	end = System.currentTimeMillis();
	System.out.println("用时：" + (end - start) + "ms");
}

}

二、改进方法代码：
byte[] buf = new byte[2048];
int length;
int read = fis.read();
while((length = fis.read(buf))!=-1){
fos.write(buf, 0, length);
}
三、测试时间代码：
File a = new File("");
File b = new File("");
long start,end;
start = System.currentTimeMillis();
copy(a,b);
end = System.currentTimeMillis();
System.out.println("用时：" + (end - start) + "ms");
四、测试结果