They are terms I'd rather avoid using. Compile-time type probably
refers to the type of a reference, whereas run-time type probably refers
to the type of an object. The concept that an object might be of a
different type than that of the reference pointing to that object is
something a lot of beginners have trouble with, I find. Consider:

Number foo = new Integer(5);

   Here, we have a reference "foo" whose type is Number, and it points to
an object whose type is Integer. The type of the reference (Number) is
different from the type of the object (Integer).

   Well... compilation occurs during the "compilation process" and
running-the-program occurs during "run-time process". This is a pretty
open-ended question, and I bet you could fill 4 books with all the
possible things that could be done during compilation and runtime (by
investigating the internals of various compilers and JVMs). I won't bother
going that detailed.

See:
http://java.sun.com/docs/books/tutorial/essential/concurrency/

You may also be interested in:
http://www.cs.indiana.edu/docproject/zen/zen-1.0_6.html#SEC56

   - Oliver

Please avoid USING ALL CAPITAL LETTERS - it gives the impression of screaming.
The proper use of capital letters is to use an upper-case letter as the first
letter of the first word of a sentence, as the first letter of proper nouns
and as each letter within most acronyms.

1)
Compile-time type is the declared type of a variable, e.g.,

List <String> strings;

At compile time the type is known to be 'List <String>'.

If you assign a particular List to that variable:

strings = new ArrayList <String> ();

then at run time, which is when the assignment happens, the run-time type of
the object is ArrayList<String>, but the variable 'strings' still has its
compile-time type of List<String>.

2)
<http://java.sun.com/docs/books/tutorial/essential/concurrency/>

You should be in the habit of looking to Sun's tutorials as a first source for
most things. After that, GIYF.

-- Lew