java之文件ＩＯ流转换为字节流

public String ioToBase64() throws IOException {
String fileName = "d:/gril.gif"; //源文件
String strBase64 = null;
try {
InputStream in = new FileInputStream(fileName);
// in.available()返回文件的字节长度
byte[] bytes = new byte[in.available()];
// 将文件中的内容读入到数组中
in.read(bytes);
strBase64 = new BASE64Encoder().encode(bytes); //将字节流数组转换为字符串
in.close();
} catch (FileNotFoundException fe) {
fe.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
}
return strBase64;
}

public void base64ToIo(String strBase64) throws IOException {
String string = strBase64;
String fileName = "d:/gril2.gif"; //生成的新文件
try {
// 解码，然后将字节转换为文件
byte[] bytes = new BASE64Decoder().decodeBuffer(string); //将字符串转换为byte数组
ByteArrayInputStream in = new ByteArrayInputStream(bytes);
byte[] buffer = new byte[1024];
FileOutputStream out = new FileOutputStream(fileName);
int bytesum = 0;
int byteread = 0;
while ((byteread = in.read(buffer)) != -1) {
bytesum += byteread;
out.write(buffer, 0, byteread); //文件写操作
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
}