In Java 8, the java.util.Base64 class was finally introduced to replace internal classes sun.misc.BASE64Encoder and sun.misc.BASE64Decoder which user code had previously had to rely on to handle Base64 encoding. With Java 11, the old internal classes have now been removed so code must be converted to the java.util.Base64 API. An example can be seen in JDK-8006182 and this changeset.

When
a Java class uses sun.misc.BASE64Encoder or sun.misc.BASE64Decoder

Perform
add a hint to replace this with java.util.Base64.getMimeEncoder() or java.util.Base64.getMimeDecoder() respectively