Java EE

Question 1

What is the difference between Java SE and Java EE?

Answer 1

SE = Standard Edition. EE = Enterprise edition; providing more tools for scalable enterprise-level applications. Enterprise Java Bean (EJB), JavaServer Pages (JSP), and Java Persistence API (JPA) can be found in Java EE.

Question 2

What is an Application Server?

Answer 2

F`ramework that provides the necessary infrastructure and runtime environment for hosting, deploying, and executing Java-based enterprise applications.

Question 3

What are Key Features of an application server?

Answer 3

Servlet Container
Enterprise JavaBeans (EJB) Container
JPA Provider
Connection Pooling
Security Services
Transaction Management
Clustering and Load Balancing

Question 4

What is a Servlet Container in the Context of Java?

Answer 4

It provides the runtime environment for deploying and executing Java servlets and JavaServer Pages (JSP). Servlet containers handle incoming HTTP requests, manage the lifecycle of servlets, and generate HTTP responses.

Question 5

What is a Enterprise JavaBeans (EJB) Container in the Context of Java?

Answer 5

It manages the lifecycle, concurrency, and transactions of Enterprise JavaBeans (EJBs), which are server-side components used for implementing business logic in Java EE applications.

Question 6

What is a JPA Provider in the Context of Java?

Answer 6

Many application servers include a Java Persistence API (JPA) provider, which facilitates object-relational mapping (ORM) and database interaction in Java EE applications.

Question 7

What is Connection Pooling in the Context of Java?

Answer 7

Application servers often provide connection pooling mechanisms to efficiently manage and reuse database connections, improving performance and scalability.

Question 8

What is a Security Services in the Context of Java?

Answer 8

Application servers offer security features such as authentication, authorization, and encryption to protect sensitive data and resources within enterprise applications.

Question 9

What is a Transaction Management in the Context of Java?

Answer 9

They support distributed transaction management, allowing multiple resources (such as databases and message queues) to participate in a single transaction, ensuring data integrity and consistency.

Question 10

What is a Clustering and Load Balancing in the Context of Java?

Answer 10

Application servers often include features for clustering and load balancing to distribute incoming requests across multiple server instances, improving scalability and fault tolerance.

Question 11

What is the difference between Global & Local variables in Java?

Answer 11

Global Variables:
Instance Scope. Known as instance variables because each instance of the object has its own copy of the instance variable.

Local Variables:
Method Scope. Only accessible within the scope in which they are declared (A method, code block, or constructer).

Question 12

What are Java Applets?

Answer 12

Java applets were a feature of the Java programming language that allowed developers to embed Java programs (applets) into web pages. Better GUIs and platform independence as long as the browser ran Java. Deprecated in Java 9.

Question 13

What is JavaFX?

Answer 13

Replaced applets. JavaFX is a modern, rich client platform for building desktop and mobile applications. New GUI Stack and developed from Swing & Abstract Window Tool Kit (AWT).

Question 14

What are Literals and what are identifiers? Can you see them here: System.out.println(“Hello” + 1 + 2.5);

Answer 14

Identifier:
An identifier in Java is a name given to a programming element such as a variable, method, class, interface, or package. NOT Reserved Keywords (void, class, public, static)
ex. System.out.println

Literal:
A literal in Java refers to a fixed value that is written directly in the source code of a program. (Hard coded and immutable)
ex. “Hello”, 1, 2.5

Question 15

What is a lexicon, lexical unit, syntax, semantics, and Tokens?

Answer 15

Lexicon - character set
Syntax - Defines Tokens
Semantics - Defines if it is syntactically correct
Lexical unit - character out of the lexicon
Token - Lexical Unit recognized by compiler

Question 16

How is Java an Imperative Language?

Answer 16

Uses statements to specify a process or flow of the program.

Question 17

Atomic Statement? Examples?

Answer 17

In programming, atomicity refers to the property of an operation being indivisible or uninterruptible. An atomic operation is one that is performed as a single, indivisible unit of work, without being affected by concurrent or interleaved operations. Atomic operations are essential for ensuring data integrity and consistency, especially in multi-threaded or concurrent programming environments

1. Assignment Statement - int x = 5;
2. Arithmetic Operation - sum = a + b;
3. Method Invocation - System.out.println(“Hello, world!”);
4. Increment/Decrement Operation - count++;
5. Empty statements - ;

Question 18

Non-Atomic Statements? Examples?

Answer 18

Non-atomic statements involve multiple steps or operations that can be divided further

1. Compound Assignment Statement - x += 10;
2. Conditional Statements - ‘if’ & ‘switch’
3. Loop Statements - for, while, and do-while

Question 19

What is a JavaBean?

Answer 19

A JavaBean is just a standard. It is a regular Java class, except it follows certain conventions:

1. All properties are private (use getters/setters)
2. A public no-argument constructor
3. Implements Serializable.

Question 20

What is Serializable?

Answer 20

Serialization in Java is the concept of representing an object’s state as a byte stream

Question 21

How does Serializable work?

Answer 21

Enabled by the class implementing the java.io.Serializable interface. Classes that do not implement this interface will not have any of their state serialized or deserialized. All subtypes of a serializable class are themselves serializable. The serialization interface has no methods or fields and serves only to identify the semantics of being serializable

Question 22

What is Serializable used for?

Answer 22

Serializable objects can be written to streams, and hence files, object databases, anything really