One of the most popular programming languages is Java. You may be able to land a job in application development if you know how to properly respond to Java interview questions. This article contains a list of 40 complex Java interview questions and answers for the benefit of learners. Explore what will be covered in our Advanced Java course syllabus.
Advanced Java Interview Questions and Answers
1. What distinguishes Core Java from Advanced Java?
By going over key subjects like Java grammar, object-oriented programming (OOP) concepts, and standard libraries, Core Java offers a foundation in Java programming.
Advanced Java is needed in many specialized fields, such as web technologies, frameworks, and Java EE (Enterprise Edition) components.
2. Which Application Types Are Created Using Java EE (J2EE)?
Enterprise-level applications are developed using Java EE, sometimes known as Java Enterprise Edition. Typical application types include the following:
- Large-scale web applications
- Enterprise resource planning (ERP) systems
Customer relationship management (CRM) systems
3. What is a servlet?
Servlets are programs that run on web or application servers and serve as a mediator between databases or applications on the HTTP server and requests from clients, such as web browsers. In other words, servlets receive requests from clients and respond to them.
4. What is the servlet life cycle?
There are three stages in the servlet lifecycle.
- Init(): This calls the init() method to initialize the servlet.
- Service(): This is how the client request is processed.
- Destroy(): This is how a servlet request is ended.
5. Define JDBC
A tool for connecting to and working with databases is called Java Database Connectivity, or JDBC. Databases and Java apps may interact due to the JDBC (Java Database Connectivity) architecture. It uses a model with two or three tiers.
- Two-tier architecture: JDBC is used to connect the database and Java application directly.
- Three-tier architecture: A middle-tier server and the Java application exchange data.
- Application: A Java servlet or applet that communicates with the data source is called an application.
- JDBC API: Java applications may run SQL queries and obtain results thanks to the JDBC API.
- DriverManager: Contributes significantly to JDBC setup. To safely link databases and enterprise apps, it makes use of certain database-specific drivers.
- JDBC Driver: A JDBC driver that intelligently connects to a compliant data source is required to use JDBC to connect to a data source.
6. What is JSP?
Java Server Pages, or JSP for short, include both HTML and JSP elements. Java code, such as scriptlet tags, is used in JSP tags.
Web applications and dynamic web content are developed using JSP, a server-side programming tool.
7. Why is garbage collection in Java used?
When an object in Java becomes unreachable to the Java application that launched it, garbage collection takes place.
Java’s garbage collection system is used to identify and eliminate things that are no longer needed by a program and are wasting program resources that could be released and put to use by other objects.
8. Lambda expressions: what are they?
Lambda expressions, or lambdas, are a new feature introduced with Java 8. They are frequently utilized in settings where programmers employ anonymous classes and offer a simpler approach to working with interfaces that only have one method.
9. Describe Java Nio.
Java.nio is a new I/O package that was introduced to the Java SDK in Java 1.4.
- As the classes in the package implemented 1/0 in a non-blocking way, the package was first presented as an extension to Java I/O.
- Additionally, the Java.nio package was designed to address some of the issues that developers can have while utilizing the Java.io classes to interact with the file system.
10. Describe Spring MVC
A component of the Spring Framework, Spring MVC offers an organized method for creating web applications. It uses a design method called Model-View-Controller (MVC), which divides an application into three primary components.
- Model: Shows the application’s data and business logic.
- View: Displays the data to the user and controls the presentation layer.
- Controller: Coordinates between the Model and the View and controls user input and interactions.
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11. Describe the distinction between the operators >> and >>>.
Despite their similar appearances, they are very different from one another.
- >> The operator shifts the sign bits to the right.
- >>> The zero-filled bits are shifted using this operator.
12. Why should we use generics in Java programming?
Generics are used to ensure compile-time type safety. Users can detect superfluous incorrect types at compilation time thanks to compile-time type safety.
Programmers can provide a single method declaration, a group of related methods, or related types with an available class declaration by using generic methods and classes.
13. Explain Daemon Thread
The thread with the lowest priority is known as the Daemon thread. During Java’s Garbage Collection, this Daemon thread is intended to operate in the background.
In Java, a Daemon thread is created using the setDaemon() function.
14. Describe the different JSP directives.
JSP Engine processes directives, which are instructions. Directives define customized tag libraries, insert external files, and specify page-level commands once the JSP page has been built into a servlet. Directives are denoted by the following symbols:
“< %@” at the beginning and “% >” at the end.
Below are examples of the different kinds of directives:
- Include Directive: It comes with a file and merges the contents of the entire file with the pages that are now active.
- Page Directive: Certain JSP page properties, such as the buffer and error page, are defined by the Page Directive.
- Taglib: The page makes use of the custom tag library that Taglib declares.
15. In Java, what is JCA?
The Java Cryptography Architecture offers an architecture, application programming interfaces, and a platform that facilitates encryption and decoding.
The Java Cryptography Architecture is used by developers to integrate the application with security applications. The Java Cryptography Architecture facilitates the use of third-party security policies and guidelines.
The security is implemented via the Java Cryptography Architecture using hash tables, encryption message digests, etc.
16. Explain JavaMail.
An API called JavaMail is frequently used in Java programming to make mailing tasks like creating, reading, sending, and receiving emails on the Internet easier.
It is a platform-independent and protocol-independent framework that is integrated into the Java EE platform and offered as an optional package with the Java SE platform.
Numerous other events can be conducted using the JavaMail API. Among its many uses are user registration (notifications such as “thank you” for visiting my website or “subscribing to our newsletter”), password forgetting (setting and updating a new password via mail), update notifications, and more.
17. Describe Java’s Polymorphism Process.
One of Java’s fundamental object-oriented features is polymorphism, which allows an object to have several forms.
- A particular work can be completed in a variety of ways thanks to this functionality.
- Essentially, polymorphism happens when several classes are related to one another.
Java exhibits polymorphism in two ways: compile-time polymorphism and runtime polymorphism.
- What is session tracking? Which session tracking techniques are most frequently used?
A session in JSP is a defined time used to track and preserve user data for a given amount of time. The web container uses a technology called session tracking to keep track of a user’s status.
Web servers and HTTP are stateless protocols. As a result, every request and answer is separate. Each request made by a user to the server is handled as though it were a brand-new one. Therefore, we employ session tracking to stop this and preserve a user’s state (identify a specific user).
The following lists the typical techniques for session tracking:
- Cookies
- HttpSession
- Hidden Form Field
- URL Rewriting
19. Describe the top five Spring Framework annotations.
- @Component: Indicates that a class is a component controlled by Spring.
- @Autowired: Dependencies are injected into a Spring bean.
- @Controller: Designates a class as a controller for Spring MVC.
- @Service: In the service layer, designates a class as a service.
- @Repository: A class is designated as a Data Access Object (DAO).
20. Define Java Transaction API (JTA)
One Java specification that supports managing transactions across many objects is the Java Transaction API (JTA).
- Transaction management: JTA makes it possible to handle transactions across a variety of resources, including message queues and databases.
- Two-Phase Commit Protocol: Makes use of a two-phase commit mechanism to guarantee that all objects’ transactions are either committed or rolled back.
- Transaction Synchronization: Offers methods for coordinating management and transaction resources, guaranteeing that every aspect of communication is connected.
- Coordination: Applications can coordinate transactions across systems or services through coordination.
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21. What Issues Is Spring Cloud Able to Address?
Cloud-native application development and deployment technologies are offered by Spring Cloud.
In a distributed system, it tackles problems including load balancing, configuration management, and service discovery.
Through fault tolerance, configuration, load balancing, solution discovery, and API administration, Spring Cloud services assist in managing microservices.
- Service Discovery: Enables applications to dynamically find one another by automatically locating and tracking services in a microservice context.
- Load Balancing: This technique divides requests across several application instances to guarantee a uniform load distribution and increase flexibility.
- Configuration Management: Allows you to configure settings without having to reinstall apps by centrally managing configuration assets for environments.
- Circuit Breaker: By identifying problems and offering backup plans, a circuit breaker strengthens the system’s resilience and stops cascading failures.
- Distributed Tracing: It makes it simpler to find and fix issues by tracking and recording requests moving between several services.
- API Gateway: Manages features like routing, authentication, and rate limiting while offering a single point of access for all microservices.
22. What does Java’s Race Condition mean?
In Java, a race condition occurs when two threads request the allocation of similar resources for execution. When two programs are operating in parallel, race situations arise when several threads request resource allocation at the same time.
23. What is the purpose of Java’s intern() method?
If a String is found in the String Pool, Java’s intern() function, which belongs to the String Class, returns a String. If not, the reference to the relevant String is returned and a new String is generated in the String pool.
24. What Do You Know About Java’s Eager Loading? How is it accomplished?
When the parent class is fetched, collections are fetched entirely thanks to a feature called eager loading. Queries to comparable entities are also run when a particular query linked with an entity is run.
The include() method can be used to achieve eager loading.
25. Define Java Data Abstraction.
Data abstraction is a feature that restricts object visibility so that users can only see and access the information or data that is required. The data abstraction feature conceals the implementation details, which users don’t need to know.
26. What distinguishes a String, StringBuffer, and StringBuilder from one another?
While the other two classes are mutable, the string class is immutable.
While StringBuilder is asynchronous, StringBuffer is synchronous.
In contrast to the other two, which use heap RAM for storage, String employs a string pool.
27. In Java, what is a comparator?
An interface that is used to sort the objects is called a comparator.
28. Explain Java Class Loading.
Java’s class loading capability allows a class’s data members to load at runtime.
Classloaders can be fetched at any point during the program cycle and are located in Java.lang package.
Three different kinds of class loaders are used in Java: system class loaders, extension class loaders, and bootstrap class loaders.
29. What distinguishes a TreeSet from a HashSet?
A hash set operates more quickly than a tree set since its items are not ordered. A hash table is used in its implementation.
30. When is the “super” keyword appropriate to use?
In essence, the parent class is referred to using the super keyword. A super keyword can be used to access data members of the parent class when the same fields are present in both the parent and child classes.
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Advanced Java Coding Interview Questions and Answers
31. Create a program to find an array list’s second-highest number.
The second-largest number in an array list can be found using the program below.
package sampleSecondHighest;
public class NextHighest {
public static void main(String[] args)
{
int array[] = { 1, 2, 3, 4, 11, 12, 13, 14, 21, 22, 23, 24, 31, 32};
int high = 0;
int nextHigh = 0;
System.out.println(“The given array is:”);
for (int i = 0; i < array.length; i++)
{
System.out.print(array[i] + “\t”);
}
for (int i = 0; i < array.length; i++)
{
if (array[i] > high)
{
nextHigh = high;
high = array[i];
}
else if (array[i] > nextHigh)
{
nextHigh = array[i];
}
}
System.out.println(“Second Highest is:” + nextHigh);
System.out.println(“Highest Number is: ” +high);
}
}
32. Describe instance variable and local variable.
While local variables are declared inside code blocks, instance variables are declared in a class but outside of methods.
//Local Variable
import Java.io.*;
class Main {
public static void main(String[] args)
{
int var = 145;
System.out.println(“Local Variable: ” + var);
}
}
//Instance variable
import Java.io.*;
class Main {
public int value = 12;
public static void main(String[] args)
{
Main va = new Main();
System.out.println(“My value is: ” + va.value);
}
}
- Is it possible to overload the primary method?
Yes, we can overload the primary method as often as we like. However, JVM prefers to use its predefined calling method to invoke the main method.
Example:
class Main {
public static void main(String args[]) {
System.out.println(” Main Method”);
}
public static void main(int[] args){
System.out.println(“Overloaded Integer array Main Method”);
}
public static void main(char[] args){
System.out.println(“Overloaded Character array Main Method”);
}
public static int main(double[] args){
System.out.println(“Overloaded Double array Main Method”);
}
public static void main(float args){
System.out.println(“Overloaded float Main Method”);
}
}
34. What are the various thread utilization methods?
In Java, a thread can be defined and implemented in two different ways. They do this by expanding the thread class and putting the runnable interface into practice.
Extending the Thread class
class InterviewBitThreadExample extends Thread{
public void run(){
System.out.println(“Thread runs…”);
}
public static void main(String args[]){
InterviewBitThreadExample ib = new InterviewBitThreadExample();
ib.start();
}
}
Implementing the Runnable interface
class InterviewBitThreadExample implements Runnable{
public void run(){
System.out.println(“Thread runs…”);
}
public static void main(String args[]){
Thread ib = new Thread(new InterviewBitThreadExample());
ib.start();
}
}
Because Java does not enable multiple inheritance of classes, it is preferable and convenient to implement a thread using the Runnable interface method.
A distinct call stack is created for thread execution by the start() procedure. The thread in the call stack is executed by the JVM using the run() method after the call stack has been constructed.
35. In Java, how is an endless loop declared?
Java allows you to declare an infinite loop by breaking the instruction block’s logic.
Example
for(int i = 1; i > 0; i++)
{
//statements
}
In Java, the code above creates an endless loop.
36. Could it be that the “finally” block won’t be carried out? List the case if the answer is yes.
Yes, there is a chance that the “finally” block won’t be able to execute. Here are a few instances where the aforementioned circumstance arises.
- When there are deadly mistakes, such as memory exhaustion, memory access issues, etc.
- Throughout the use of System.exit()
37. Create a program that eliminates duplicate entries from an array list.
To eliminate duplicate elements from an ArrayList, run the following program.
package sampleDuplicateJava;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
public class ArrayDuplicate {
public static void main(String args[]) {
List<Integer> num = new ArrayList<Integer>();
num.add(1);
num.add(2);
num.add(3);
num.add(4);
num.add(5);
num.add(6);
num.add(3);
num.add(4);
num.add(5);
num.add(6);
System.out.println(“Your list of elements in ArrayList : ” + num);
Set<Integer> primesWithoutDuplicates = new LinkedHashSet<Integer>(num);
num.clear();
num.addAll(primesWithoutDuplicates);
System.out.println(“list of original numbers without duplication: ” + num);
}
}
38. Create a program that recognizes a string’s duplicate characters.
Below is the code for the program that detects duplicate elements in a string:
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class FindDuplicate {
public static void main(String args[]) {
printDuplicateCharacters(“Simplilearn”);
}
public static void printDuplicateCharacters(String word) {
char[] characters = word.toCharArray();
Map<Character, Integer> charMap = new HashMap<Character, Integer>();
for (Character ch : characters) {
if (charMap.containsKey(ch)) {
charMap.put(ch, charMap.get(ch) + 1);
} else {
charMap.put(ch, 1);
}
}
Set<Map.Entry<Character, Integer>> entrySet = charMap.entrySet();
System.out.printf(“List of duplicate characters in String ‘%s’ %n”, word);
for (Map.Entry<Character, Integer> entry : entrySet) {
if (entry.getValue() > 1) {
System.out.printf(“%s: %d %n”, entry.getKey(), entry.getValue());
}
}
}
}
39. Use recursion to implement binary search in Java.
// Java Program to Demonstrate Recursive Binary Search
// Importing Necessary Classes
import java.util.*;
// Main class
class GFG {
// Method 1
// Recursive binary search
// Returns index of x if it is present
// in arr[l..r], else return -1
int binarySearch(int arr[], int l, int r, int x)
{
// Restrict the boundary of right index
// and the left index to prevent
// overflow of indices
if (r >= l && l <= arr.length – 1) {
int mid = l + (r – l) / 2;
// If the element is present
// at the middle itself
if (arr[mid] == x)
return mid;
if (arr[mid] > x)
return binarySearch(arr, l, mid – 1, x);
return binarySearch(arr, mid + 1, r, x);
}
return -1;
}
public static void main(String args[])
{
GFG ob = new GFG();
int arr[] = { 2, 3, 4, 10, 40 };
int n = arr.length;
int x = 10;
int result = ob.binarySearch(arr, 0, n – 1, x);
if (result == -1)
// Print statement
System.out.println(“Element not present”);
else
System.out.println(“Element found at index “
+ result);
}
}
40. Create Java software that uses user-inputted matrices to rotate arrays 90 degrees clockwise.
public class RotateMatrixClockwise
{
public static void main(String args[])
{
int a[][]= {{1,2,3},{4,5,6},{7,8,9}};
System.out.println(“Original Matrix: \n”);
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
System.out.print(” “+a[i][j]+”\t”);
}
System.out.println(“\n”);
}
System.out.println(“Rotate Matrix by 90 Degrees Clockwise: \n”);
for(int i=0;i<3;i++)
{
for(int j=2;j>=0;j–)
{
System.out.print(“”+a[j][i]+”\t”);
}
System.out.println(“\n”);
}
}
}
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Conclusion
Before going to an interview, it is crucial to review the Java interview questions. They help you prepare for the questions that will be asked during your interview, so you can be comfortable. Fine-tune your skills with our advanced Java interview questions and answers. Gain expertise with hands-on exposure with our advanced Java training in Chennai.
