answer 37)

4) -3.0

answer 38)

3) one

command line parameters start from 0 and from the first parameter after the name of the compile (normally java)

answer 39)

4) the set is designed for unique elements.

collection is an interface, not a class. the collection interface includes a method called iterator. this returns an instance of the iterator class which has some similarities with enumerators.
the name set should give away the purpose of the set interface as it is analogous to the set concept in relational databases which implies uniquness.

answer 40)

2) if multiple listeners are added to a component the events will be processed for all but with no guarantee in the order
4) you may remove as well add listeners to a component.

it ought to be fairly intuitive that a component ought to be able to have multiple listeners. after all, a text field might want to respond to both the mouse and keyboard

answer 41)

1) b=m;
3) d =i;

you can assign up the inheritance tree from a child to a parent but not the other way without an explicit casting. a boolean can only ever be assigned a boolean value.

answer 42)

2) you can obtain a mutually exclusive lock on any object
3) a thread can obtain a mutually exclusive lock on an object by calling a synchronized method on that object.
4) thread scheduling algorithms are platform dependent

yes that says dependent and not independent.