What is the force view? What is the use of force view?
The definition of force in the "Create View" statement according to the Oracle docs is:
Specify FORCE if you want to create the view regardless of whether the base tables of the view or the referenced object types exist or the owner of the schema containing the view has privileges on them. These conditions must be true before any SELECT, INSERT, UPDATE, or DELETE statements can be issued against the view. If the view definition contains any constraints, CREATE VIEW ... FORCE will fail if the base table does not exist or the referenced object type does not exist. CREATE VIEW ... FORCE will also fail if the view definition names a constraint that does not exist.
I think a good use of the force parameter in the create view statement is when you are executing a script that has create tables and views statements. By using the force parameter, it does not matter which order the views are created, either before the create table statement or after the create table statement.