Tell me the difference between a queue and a stack?
Stacks are working by last-in-first-out rule (LIFO), and the queues are using the FIFO rule.
Can we use abstract classes instead of interfaces?
Sometimes. But the class may be a descendent of another class and in this case the interface is the only option.
Uses of "this" and "super"?
"this" is used to refer to the current object instance." super" is used to refer to the variables and methods of the superclass of the current object instance.
Define synchronized methods.
The Synchronized methods are methods that are used to control access to an object.Here the thread only executes a synchronized method after it has acquired the lock for the method's object or class.
Define Synchronized Statements.
The Synchronized statements are similar to synchronized methods. This can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
Define Collection interface?

It provides the support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.

Define task's priority.

A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks

Describe Collections API?

It is a set of classes and interfaces that support operations on collections of objects.

Is it possible, for statement loop indefinitely?

Yes, a for statement can loop indefinitely.

Tell me which method is used to specify a container's layout.

The setLayout() method is used to specify a container's layout.