When I used the apktool tool to sign an APK, I hit a sun/misc/BASE64Encoder error.
The reason is that this class only exists in versions before jdk1.8; from jdk9 onwards it no longer exists.
The JDK version in the environment I checked was 11, so the error shows up.
The fix is clear as well: install JDK8.
Here is a one-command way to install JDK8 on Windows 10 — just run the following in a cmd window:
winget install AdoptOpenJDK.OpenJDK.8
After installation, the JDK is located at C:\Program Files\AdoptOpenJDK\jdk-8.0.292.10-hotspot