What is the difference between Java EE and Java SE?

Java SE (Standard Edition) is the core Java platform, while Java EE (Enterprise Edition) provides additional features for enterprise-level application development, such as distributed computing and web services.

What are the primary data storage options in Java Backend?

Primary data storage options include relational databases (MySQL, PostgreSQL), NoSQL databases (MongoDB, Cassandra), and in-memory databases (Redis, Hazelcast).

What is the role of a Java Backend Developer?

A Java Backend Developer designs, develops, and maintains server-side logic, database interactions, and application architecture using Java technologies.

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import java.util.Arrays;
import java.util.LinkedHashSet;

public class ArrayExample
{
    public static void main(String[] args) throws CloneNotSupportedException
    {
        //Array with duplicate elements
        Integer[] numbers = new Integer[] {1,2,3,4,5,1,3,5};
        
        //This array has duplicate elements
        System.out.println( Arrays.toString(numbers) );
        
        //Create set from array elements
        LinkedHashSet<Integer> linkedHashSet = new LinkedHashSet<>( Arrays.asList(numbers) );
        
        //Get back the array without duplicates
        Integer[] numbersWithoutDuplicates = linkedHashSet.toArray(new Integer[] {});
        
        //Verify the array content
        System.out.println( Arrays.toString(numbersWithoutDuplicates) );
    }
}

--- ---Streams-------
Stream API is introduced in Java 8 and is used to process collections of objects with the functional style of coding using the lambda expression. So to understand what stream API is, you must have knowledge of both lambda and functional interfaces.

Comparable and Comparator
-----------------------------------------
Comparable and Comparator are interfaces used to order objects. They are particularly useful in sorting operations and collections that require natural ordering. Here we will learn about Comparable and Comparator in depth.

-------Date/Time API--------
This section gives you to handle the ever-changing world of dates and times within your Java programs. Explore working with calendars, timestamps and time manipulation – essential skills for building applications that deal with deadlines, scheduling or even historical data analysis.

What is Functional Interface in Java 8?

An interface with only one abstract method is known as a functional interface but there is no restriction, in a functional interface you can have n number of default methods and static methods.

When to use map and flatMap?

map(): It is used where we have to map the elements of a particular collection to a specific function, and then we need to return the stream that contains the updated results.
Example: Multiply all the elements of a list by 3 and return the updated list.
flatMap(): It is used where we have to transform or flatten the string, as we can't flatten our string using map().
Example: Get the first Character of all the String present in a List of Strings and return the result in form of a stream.

 '==' vs '.equals()': A common interview trap
This distinction catches many freshers off guard.
For primitive types, == performs value comparison. But for objects, it only checks if two references point to the same memory address. To compare object values properly, use .equals(), many classes override this method to provide meaningful comparisons.

Wrapper classes: Why they matter ?

Wrapper classes convert primitives (int, boolean, etc.) into objects. You need them because:
• Collections like ArrayList only store objects, not primitives. 
• They provide utility methods for type conversions.
• They let you use primitives where objects are required.
Each primitive has its wrapper: int → Integer, double → Double, char → Character, and so on.