Is null a keyword?

The null value is not a keyword.

What's new with the stop(), suspend() and resume() methods in JDK 1.2?

The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.

Can a lock be acquired on a class?

Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.

What is synchronization and why is it important?

With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.

How are Observer and Observable used?

Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.

Why do threads block on I/O?

Threads block on i/o (that is enters the waiting state) so that other threads may execute while the i/o Operation is performed.

which containers use a border Layout as their default layout?

The window, Frame and Dialog classes use a border layout as their default layout.

what is a transient variable?

A transient variable is a variable that may not be serialized.

JAVA

"Java" generally refers to a combination of three things: the Java programming language (a high-level, object-oriented programming language); the Java Virtual Machine (a high-performance virtual machine that executes bytecodes on a specific computing platform, typically abbreviated JVM); and the Java platform, a JVM running compiled Java bytecodes, usually calling on a set of standard libraries such as those provided by Java Standard Edition (SE) or Enterprise Edition (EE). Though coupled by design, the language does not imply the JVM, and vice versa.