java.lang.IllegalArgumentException: Illegal base64 character a

I have this string data to base64 decode

String mfstr = "BZCaRm9ChAbA58sgSwlhzgVuPwboh2qvgcPuLxKJkLpesdHvyZtaheThUSw6%2BHItGBtgimHpXqbn%0ApggBaRR2wisjNiyQrX03eEJlet6%2BqFL6TouRr0wW3NLRZSHOHUSFtJkpq0cyXy%2FSfMVB47y93xlq%0Az845uXSTK2Vi%2FgzwFVphHd%2BTK%2FrO%2FDxJ4EfvAoW0zxeYS%2BCWnIsl%2F4ILehVYasGtxC%2FjbG1I8S%2Fc%0AZoqXIcPmPWrszbG7R1ouDQ473TyCMLx9PBsl1Z%2Bj39V4Qr01ZRw7GVP2m%2Bk4xrHg2Im1OuXpd2vl%0AKGwe5j2T1ZHtoYxCvXOOU1YeJYSR%2Ff7Kd7KbpnjvFT2Ua%2FOdHx%2FKzBoK3Yk97fdvMcelUGMxveKq%0A8C9aCXFVU1xjK81CwB72QWkK5%2B8DCjItVDFcpnVFnhk8ZwlYKU6o8jETDockNMKiDmBYqKGpnNII%0ACnQBGiWy0inWj40k8VoFNIuVK1yYzLoVvFrYR514Ex6U2AK00c0f7C2C5vISsOEp%2BW8KHG2hFW7G%0A97IgwnX3vtQc0s0SaZ%2B7SPgbxwUujlULaOa0t5W9ZDs9b7jDyBZA7m8DiFrLH2YpzpBhrHXcw%2B%2BZ%0A";

String carg = URLDecoder.decode(mfstr, "UTF-8");

byte[] v5 = Base64.getDecoder().decode(carg.getBytes());

when I ran this code I am getting the error: java.lang.IllegalArgumentException: Illegal base64 character a, I have tried so far to pass StandardCharsets.UTF_8 in carg.getBytes() But nothing. what am I doing wrong here?

the answer will be just to get a way to remove those line breaks as they are not valid base64 characters. I changed the code as follows:

String mfstr = "BZCaRm9ChAbA58sgSwlhzgVuPwboh2qvgcPuLxKJkLpesdHvyZtaheThUSw6%2BHItGBtgimHpXqbn%0ApggBaRR2wisjNiyQrX03eEJlet6%2BqFL6TouRr0wW3NLRZSHOHUSFtJkpq0cyXy%2FSfMVB47y93xlq%0Az845uXSTK2Vi%2FgzwFVphHd%2BTK%2FrO%2FDxJ4EfvAoW0zxeYS%2BCWnIsl%2F4ILehVYasGtxC%2FjbG1I8S%2Fc%0AZoqXIcPmPWrszbG7R1ouDQ473TyCMLx9PBsl1Z%2Bj39V4Qr01ZRw7GVP2m%2Bk4xrHg2Im1OuXpd2vl%0AKGwe5j2T1ZHtoYxCvXOOU1YeJYSR%2Ff7Kd7KbpnjvFT2Ua%2FOdHx%2FKzBoK3Yk97fdvMcelUGMxveKq%0A8C9aCXFVU1xjK81CwB72QWkK5%2B8DCjItVDFcpnVFnhk8ZwlYKU6o8jETDockNMKiDmBYqKGpnNII%0ACnQBGiWy0inWj40k8VoFNIuVK1yYzLoVvFrYR514Ex6U2AK00c0f7C2C5vISsOEp%2BW8KHG2hFW7G%0A97IgwnX3vtQc0s0SaZ%2B7SPgbxwUujlULaOa0t5W9ZDs9b7jDyBZA7m8DiFrLH2YpzpBhrHXcw%2B%2BZ%0A";

String carg = URLDecoder.decode(mfstr, "UTF-8");

carg = carg.replace("\n","");

byte[] v5 = Base64.getDecoder().decode(carg.getBytes());

Thanks @Tom for the head up discussion.