I use kotlin. I had to add line implementation("com.google.protobuf:protobuf-java:3.24.0") to my build.gradle.kts to make qdrant java-client works.
Now I have this 2 lines:
implementation("io.qdrant:client:1.9.1")
implementation("com.google.protobuf:protobuf-java:3.24.0")
Secund think, I had to use exacly version 3.24.0, witch is pointed in https://github.com/qdrant/java-client/blob/master/build.gradle#L81
Maybe it because kotlin, but I think it is worth to say it in documentation.