Java Interview Questions
1 .
What is auto boxing?
Converting a primitive data type into an object form automatically is called auto boxing. Auto boxing is done in generic types. 
2 .
What is the difference between Stack and LinkedList?
• A Stack is generally used for the purpose of evaluation of expressions. A LinkedList is used to store and retrieve data.
• Insertion and deletion of elements only from the top of the Stack is possible. Insertion and deletion of elements from anywhere is possible in case of a LinkedList.
3 .
What is the difference between ArrayList and Vector?
•   ArrayList is not synchronized by default hence it should not be used with multiple threads. Vector is synchronized by default hence it can be used with single thread (or) multiple threads.
•   ArrayList works fast while working with single thread whereas Vector works slow while working with single thread.
4 .
Can you synchronize the ArrayList object?
Yes, we can use synchronizedList() method to synchronize the ArrayList as:
Collections.synchronizedList(new ArrayList());
5 .
What is the load factor foe a HashMap or Hashtable?
0.75
6 .
What is the difference between HashMap and Hashtable?
•  HashMap object is not synchronized by default whereas Hashtable object is synchronized by default.
•  In case of single thread, using HashMap is faster than the Hashtable, whereas in the case of multiple threads, using Hashtable is advisable. With a single thread, Hashtable becomes slow.
•  HashMap allows null keys and null values to be stored Whereas Hashtable does not allow null keys and null values.
7 .
Can you make HashMap synchronized?
Yes, we can make HashMap object synchronized using synchronizedMap() method as shown here :   
Collections.synchrnizedMap(new HashMap());
8 .
what is java AWT?
AWT stands for Abstract Window Toolkit. AWT enables programmers to develop Java applications with GUI components, such as windows, and buttons. The Java Virtual Machine (JVM) is responsible for translating the AWT calls into the appropriate calls to the host operating system.
9 .
what is the difference between a window and a frame?
A window is a frame without any borders and title, where as a frame contains borders and title.
10 .
what is event delegation model?
Event delegation model represents that when an event is generated by the user on a component, it is delegated to a listener interface and the listener calls a method in response to the event. Finally, the event is handled by the method.