I hope it would be clear now, after tamilselvan had explicitly defined things. Answering to one of your other questions of java_pool_size, the 20M seems to be the default one and you do not want to further reduce that size, b'cos it might cause the problem at the time of starting the instance. If you would like, you can go ahead and increase it, but not reduce it if you have any of the oracle intermedia and other stuff that were installed by default.

to see whether the java components have been installed in the database, try doing

describe dbms_java


Good luck,
Sam