Java Interview Questions 23

111. Question: Name the containers which uses Border Layout as their default
layout?
Answer: Containers which uses Border Layout as their default are: window, Frame and
Dialog classes.

112. Question: What do you understand by Synchronization?
Answer: Synchronization is a process of controlling the access of shared resources
by the multiple threads in such a manner that only one thread can access one
resource at a time. In non synchronized multithreaded application, it is possible
for one thread to modify a shared object while another thread is in the process of
using or updating the object's value. Synchronization prevents such type of data
corruption.
E.g. Synchronizing a function:
public synchronized void Method1 () {
// Appropriate method-related code.
}
E.g. Synchronizing a block of code inside a function:
public myFunction (){
synchronized (this) {
// Synchronized code here.
}
}

113. Question: What is Collection API?
Answer: The Collection API is a set of classes and interfaces that support
operation on collections of objects. These classes and interfaces are more
flexible, more powerful, and more regular than the vectors, arrays, and hashtables
if effectively replaces.
Example of classes: HashSet, HashMap, ArrayList, LinkedList, TreeSet and TreeMap.
Example of interfaces: Collection, Set, List and Map.

114. Question: Is Iterator a Class or Interface? What is its use?
Answer: Iterator is an interface which is used to step through the elements of a
Collection.

115. Question: What is similarities/difference between an Abstract class and
Interface?
Answer: Differences are as follows:
• Interfaces provide a form of multiple inheritance. A class can extend only
one other class.
• Interfaces are limited to public methods and constants with no
implementation. Abstract classes can have a partial implementation, protected
parts, static methods, etc.
• A Class may implement several interfaces. But in case of abstract class, a
class may extend only one abstract class.
• Interfaces are slow as it requires extra indirection to to find
corresponding method in in the actual class. Abstract classes are fast.
Similarities:
• Neither Abstract classes or Interface can be instantiated.