What is the effect of static final transient in Java?

A static field is implicitly transient (when serializing a static field, its value will be lost anyway). So indeed, no need to declare both.

The transient keyword on a variable will ensure that the variable is not part of the serialized object when serializing. If your class is not serializable, nor a JPA entity (which uses the transient keyword to avoid storing variables in the database), removing it should be fine.