java基于IO流的文件复制

不带字节缓冲区的文件复制

public static void main(String[] args) throws IOException {
        //字节数组大小
        int length = 1024;
        
        FileInputStream fis = new FileInputStream("C:\\Users\\asus\\Desktop\\yuanwenjian .pdf");
        FileOutputStream fos = new FileOutputStream("C:\\Users\\asus\\Desktop\\co.pdf");

        long begin = System.currentTimeMillis();
        int len = 0;
        byte[] bytes = new byte[length];
        while ((len = fis.read(bytes)) != -1){
            fos.write(bytes,0,len);
        }
        fos.close();
        fis.close();
        long end = System.currentTimeMillis();
        System.out.println("耗时:"+(end - begin)+"ms");
    }

带字节缓冲区的文件复制

public static void main(String[] args) throws IOException {
        //缓冲区大小
        int length1 = 100000;
        //字节数组大小
        int length2 = 100000;

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("C:\\Users\\asus\\Desktop\\源文件 .pdf"),length1);
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("C:\\Users\\asus\\Desktop\\copy.pdf"),length1);

        long b = System.currentTimeMillis();
        int len = 0;
        byte[] bytes = new byte[length2];
        while ((len = bis.read(bytes)) != -1){
            bos.write(bytes,0,len);
        }
        //先释放输出,后释放输入.
        bos.close();
        bis.close();
        long e = System.currentTimeMillis();

        System.out.println("耗时:"+(e-b)+"ms");
    }

随着字节数组和缓冲区大小的改变,复制效率也会跟着改变.