java将InputStream转换成字节数组

public class InputStream2ByteArray {

    public static void main(String[] args) throws IOException {
        InputStream in=new FileInputStream("/tmp/req.data");
        byte[] data=toByteArray(in);
        in.close();
        FileOutputStream out=new FileOutputStream("/tmp/req2.data");
        out.write(data);
        out.close();
    }

    public static byte[] toByteArray(InputStream in) throws IOException {
        ByteArrayOutputStream out=new ByteArrayOutputStream();
        byte[] buffer=new byte[1024*4];
        int n=0;
        while ( (n=in.read(buffer)) !=-1) {
            out.write(buffer,0,n);
        }
        return out.toByteArray();
    }
}