Java 8 | OOP | SQL | Programming Logic

Duration: 20 Minutes

Experience: 2–6 Years

This assessment is intended for a quick technical screening of Java Backend Developers before proceeding to detailed technical interviews.

Skills Tested:

OOPS
Overloading & Overriding
Static methods
Java 8 Functional Interfaces
Exception Handling
SQL
Programming Logic

Section A – Java OCP Style MCQs (5 Questions)

Question 1 – Static Method Hiding

What is the output?

class Parent {

    static void print() {
        System.out.print("Parent ");
    }
}

class Child extends Parent {

    static void print() {
        System.out.print("Child ");
    }
}

public class Test {

    public static void main(String[] args) {

        Parent p = new Child();
        p.print();

    }

}

A. Parent

B. Child

C. Parent Child

D. Compilation Error

Question 2 – Method Overloading

public class Test {

    static void display(Object obj){
        System.out.print("Object ");
    }

    static void display(String str){
        System.out.print("String ");
    }

    public static void main(String[] args){

        display(null);

    }

}

Output?

A. Object

B. String

C. Compilation Error

D. NullPointerException

Question 3 – Method Overriding

class Animal {

    void sound(){
        System.out.print("Animal ");
    }

}

class Dog extends Animal{

    void sound(){
        System.out.print("Dog ");
    }

}

public class Test{

    public static void main(String[] args){

        Animal a=new Dog();

        a.sound();

    }

}

A. Animal

B. Dog

C. Compilation Error

D. Runtime Exception

Question 4 – Functional Interface

@FunctionalInterface
interface Operation{

    int calculate(int a,int b);

}

public class Test{

    public static void main(String[] args){

        Operation op=(a,b)->a*b;

        System.out.println(op.calculate(4,5));

    }

}

Output?

A. 9

B. 20

C. Compilation Error

D. Runtime Exception

Question 5 – Exception Handling

public class Test{

    public static void main(String[] args){

        try{

            System.out.print("A ");
            throw new RuntimeException();

        }
        catch(Exception e){

            System.out.print("B ");

        }
        finally{

            System.out.print("C");

        }

    }

}

Output?

A. A B C

B. A C

C. B C

D. RuntimeException

Section B – SQL (1 Question)

Question 6

Table:

EMP_ID	NAME	DEPT	SALARY
1	John	IT	5000
2	Mary	HR	6000
3	Steve	IT	7000
4	David	HR	4000
5	Tom	IT	5500

Query

SELECT DEPT,
       COUNT(*)
FROM EMPLOYEE
GROUP BY DEPT
HAVING AVG(SALARY)>5500;

Output?

IT 3

HR 2

IT 3
HR 2

No Rows

Section C – Programming (3 Questions)

Question 7 – String Logic

Write a Java program to check whether two strings are anagrams.

Example

listen
silent

Output

true

Question 8 – Collections & Java 8

Given

List<Integer> list =
Arrays.asList(2,5,8,3,4,2,8);

Using Java 8 (preferred), write a program to:

Remove duplicates
Print only even numbers
Sort in descending order

Expected Output

8
4
2

Question 9 – Programming Logic

Write a Java program to reverse every word in the sentence while preserving the word order.

Example

Java Backend Interview

Expected Output

avaJ dnekcaB weivretnI

Bonus: Solve without using StringBuffer.reverse().

Answer Key

Q	Answer
1	A
2	B
3	B
4	B
5	A
6	A

Evaluation Guide

Score	Rating
9/9	Excellent – Strong Java 8 Developer
7–8	Good – Recommended for Technical Round
5–6	Average – Needs Deeper Evaluation
Below 5	Not Recommended

Answer Key & Detailed Explanations

Section A – Java OCP Style MCQs

Question 1 – Static Method Hiding

Correct Answer: A. Parent

Explanation

Parent p = new Child();
p.print();

Static methods are hidden, not overridden.

The method that executes depends on the reference type, not the object type.

Since p is of type Parent, Parent.print() is called.

Key Concept: Static methods are resolved at compile time.

Question 2 – Method Overloading

Correct Answer: B. String

Explanation

The compiler finds two overloaded methods:

display(Object obj)
display(String str)

When null is passed, both methods are applicable.

Java always selects the most specific overload, which is String.

Key Concept: Overloading is resolved at compile time.

Question 3 – Method Overriding

Correct Answer: B. Dog

Explanation

Animal a = new Dog();
a.sound();

This is runtime polymorphism.

Although the reference is Animal, the actual object is Dog, therefore Java invokes:

Dog.sound()

Key Concept: Overridden instance methods are resolved at runtime.

Question 4 – Functional Interface

Correct Answer: B. 20

Explanation

The lambda expression

(a,b) -> a * b

implements the single abstract method of the functional interface.

4 × 5 = 20

Output:

Key Concept: A Functional Interface contains exactly one abstract method and can be implemented using a lambda expression.

Question 5 – Exception Handling

Correct Answer: A. A B C

Explanation

Execution sequence:

try
 ↓
Print A
 ↓
Throw RuntimeException
 ↓
catch
 ↓
Print B
 ↓
finally
 ↓
Print C

Output

A B C

Key Concept: The finally block executes whether or not an exception occurs (except in a few JVM termination scenarios).

Section B – SQL

Question 6

Correct Answer: A

Query

SELECT DEPT,
       COUNT(*)
FROM EMPLOYEE
GROUP BY DEPT
HAVING AVG(SALARY) > 5500;

Step 1 – Group Data

Department	Employees	Average Salary
IT	5000,7000,5500	5833.33
HR	6000,4000	5000

Step 2 – Apply HAVING

5833 > 5500  ✓

5000 > 5500  ✗

Only IT satisfies the condition.

Output

IT   3

Interview Concepts Tested

GROUP BY
Aggregate Functions
HAVING clause
SQL execution order

Execution order:

FROM

GROUP BY

HAVING

SELECT

Section C – Programming Questions

Question 7 – Anagram

Sample Solution (Java 8)

import java.util.Arrays;

public class Test {

    public static void main(String[] args) {

        String s1 = "listen";
        String s2 = "silent";

        char[] a = s1.toCharArray();
        char[] b = s2.toCharArray();

        Arrays.sort(a);
        Arrays.sort(b);

        System.out.println(Arrays.equals(a, b));

    }

}

Output

true

Alternate Approach

Use HashMap<Character,Integer>
Count frequency of every character

Complexity

Time: O(n log n)

Space: O(n)

Question 8 – Collections & Java 8

Sample Solution

import java.util.Arrays;

public class Test {

    public static void main(String[] args) {

        Arrays.asList(2,5,8,3,4,2,8)
                .stream()
                .distinct()
                .filter(n -> n % 2 == 0)
                .sorted((a,b) -> b-a)
                .forEach(System.out::println);

    }

}

Output

8
4
2

Java 8 Concepts Tested

Streams
distinct()
filter()
sorted()
Lambda Expressions
Method References

Complexity

Time: O(n log n)

Space: O(n)

Question 9 – Reverse Every Word

Sample Solution

public class Test {

    public static void main(String[] args) {

        String input = "Java Backend Interview";

        String[] words = input.split(" ");

        for(String word : words){

            for(int i = word.length()-1; i >= 0; i--){

                System.out.print(word.charAt(i));

            }

            System.out.print(" ");

        }

    }

}

Output

avaJ dnekcaB weivretnI

Bonus Java 8 Solution

import java.util.Arrays;

public class Test {

    public static void main(String[] args) {

        String input = "Java Backend Interview";

        Arrays.stream(input.split(" "))
              .map(s -> new StringBuilder(s)
              .reverse()
              .toString())
              .forEach(s -> System.out.print(s + " "));

    }

}

Complexity

Time: O(n)

Space: O(n)

Interview Evaluation Notes

Candidates who answer correctly should be able to explain why, not just provide the output.

Question	Skill Being Tested
Q1	Static method hiding vs overriding
Q2	Method overloading resolution
Q3	Runtime polymorphism
Q4	Functional Interface & Lambda
Q5	Exception handling and finally block
Q6	SQL execution order, GROUP BY, HAVING
Q7	String manipulation, Arrays, Algorithm
Q8	Collections, Streams, Lambda, Sorting
Q9	Loops, Strings, Java 8 thinking

Scoring Rubric

Score	Recommendation
9/9	Excellent. Strong Java developer with good problem-solving ability.
7–8	Good. Suitable for the next technical round.
5–6	Average. Understands fundamentals but needs deeper evaluation.
Below 5	Significant gaps in Java fundamentals; not recommended for backend Java roles.

Java 8 | OOP | SQL | Programming Logic

Section A – Java OCP Style MCQs (5 Questions)

Question 1 – Static Method Hiding

Question 2 – Method Overloading

Question 3 – Method Overriding

Question 4 – Functional Interface

Question 5 – Exception Handling

Section B – SQL (1 Question)

Question 6

Section C – Programming (3 Questions)

Question 7 – String Logic

Question 8 – Collections & Java 8

Question 9 – Programming Logic

Answer Key

Evaluation Guide

Answer Key & Detailed Explanations

Section A – Java OCP Style MCQs

Question 1 – Static Method Hiding

Explanation

Question 2 – Method Overloading

Explanation

Question 3 – Method Overriding

Explanation

Question 4 – Functional Interface

Explanation

Question 5 – Exception Handling

Explanation

Section B – SQL

Question 6

Step 1 – Group Data

Step 2 – Apply HAVING

Interview Concepts Tested

Section C – Programming Questions

Question 7 – Anagram

Sample Solution (Java 8)

Alternate Approach

Complexity

Question 8 – Collections & Java 8

Sample Solution

Java 8 Concepts Tested

Complexity

Question 9 – Reverse Every Word

Sample Solution

Bonus Java 8 Solution

Complexity

Interview Evaluation Notes

Scoring Rubric

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