Why Java Pool is not a required component of Oracle SGA?
Java inside the database is optional. If it is not installed, why waste memory on it?

Since 11.2.0.4, it is possible to "disable" it if patch 20681008 is installed, with the below parameter:

"_bug20681008_force_java_pool_zero" = true


Starting with 12.2, the below can be used:

"_force_java_pool_zero" = true