如何將InputStream轉化爲base64

/** 
 * @author 
 * @date   
 * @version 1.0   
 */
public class FileToBase64 {
    public static String getBase64FromInputStream(InputStream in) {
        // 將圖片文件轉化爲字節數組字符串，並對其進行Base64編碼處理
        byte[] data = null;
        // 讀取圖片字節數組
        try {
            ByteArrayOutputStream swapStream = new ByteArrayOutputStream();
            byte[] buff = new byte[100];
            int rc = 0;
            while ((rc = in.read(buff, 0, 100)) > 0) {
                swapStream.write(buff, 0, rc);
            }
            data = swapStream.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return new String(Base64.encodeBase64(data));
    }
}