Java Programming Real Interview Coding Exercises
Date: 4 September 2026 | Posted by: voska89
Java Programming Real Interview Coding Exercises
Published 8/2026
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Build Java problem-solving skills with beginner to advanced Hands on coding exercises and practical programming tasks.
What you'll learn
Solve Java programming problems using variables, operators, conditions, loops, methods, and recursion.
Apply object-oriented programming concepts including classes, inheritance, interfaces, and polymorphism.
Practise Java collections, generics, exception handling, file operations, and modern Java APIs.
Implement Java Stream API solutions using lambdas, functional interfaces, filtering, mapping, and reduction.
Build solutions for concurrency problems using threads, executors, synchronization, and virtual threads.
Practise modern Java 21 features including records, sealed classes, pattern matching, and sequenced collections.
Improve coding problem-solving skills through structured Java exercises with increasing difficulty.
Identify programming gaps and strengthen Java coding confidence through repeated hands-on practice.
Requirements
Basic understanding of programming concepts such as variables, data types, and logic is helpful.
Familiarity with Java syntax is recommended but not mandatory for learners starting from fundamentals.
A computer with Java Development Kit (JDK) installed is recommended for practising solutions.
Learners should be willing to write, test, debug, and improve Java code.
Basic object-oriented programming knowledge is helpful for intermediate and advanced sections.
Description
Build stronger Java programming skills through structured hands-on coding practice. This course is designed for learners who want to improve their ability to write, analyse, debug, and solve Java programming problems through practical exercises.
Java knowledge improves through consistent practice. Instead of only studying concepts, you will apply Java programming techniques by solving carefully structured coding challenges that progress from beginner foundations to advanced development concepts.
Build Practical Java Programming Skills Through Hands-On Challenges
In this course, you will practise
• Java variables, operators, conditions, loops, methods, and recursion
• Arrays, strings, and problem-solving techniques
• Object-oriented programming concepts including classes, inheritance, interfaces, and polymorphism
• Collections Framework including List, Set, Map, and generics
• Exception handling, regular expressions, file handling, and Java date/time APIs
• Lambda expressions and Stream API operations
• Multithreading, concurrency concepts, executors, and modern Java 21 features
The exercises are structured across different difficulty levels, helping you gradually improve your coding ability and confidence.
What You Will Practise
You will solve programming challenges involving
• Mathematical operations and logical problem solving
• String and array manipulation
• Object-oriented design problems
• Collection-based programming tasks
• Generic programming solutions
• Functional programming approaches
• Concurrent programming scenarios
• Modern Java language features
The course includes exercises progressing from beginner-level Java fundamentals to advanced topics such as streams, concurrency, virtual threads, records, sealed classes, and pattern matching.
Who Should Take This Course?
This course is suitable for
• Beginners learning Java programming
• Students preparing for coding interviews
• Developers wanting additional Java practice
• Programmers revising core and advanced Java concepts
• Anyone looking for structured Java coding challenges
This course focuses on practical implementation. You will spend your time writing code, analysing solutions, and improving your programming approach.
How To Use This Course
Recommended learning approach
- Start with beginner exercises to strengthen Java foundations.
- Attempt each challenge before reviewing solutions.
- Analyse mistakes and understand alternative approaches.
- Practise weaker programming areas repeatedly.
- Continue progressing through intermediate and advanced challenges.
Consistent coding practice is one of the most effective ways to improve programming skills.
Sample Coding Exercise
Student Average and Grade Object
EXERCISE OVERVIEW
Exercise Title
Student Average and Grade Object
Topic
Object-Oriented Programming
PLAN EXERCISE — LEARNING OBJECTIVE
Learning Objective
Create a Student object that stores a name and scores, calculates the average, and returns a letter grade using A≥90, B≥80, C≥70, D≥60, otherwise F.
Challenge
Create a Student object that stores a name and scores, calculates the average, and returns a letter grade using A≥90, B≥80, C≥70, D≥60, otherwise F.
Your Task
Implement the required Java type or types exactly as specified. Keep the required class, interface, enum, record, constructor, and method names unchanged so the JUnit evaluation can call them.
Method SignatureJAVACopy
Student(String name, double[] scores)
String getName()
double calculateAverage()
char getGrade()
Input
- name (String): student name.
- scores (double[]): zero or more values in the range 0–100.
Return Value
calculateAverage() returns the arithmetic mean, or 0.0 for an empty array. getGrade() returns A, B, C, D, or F.
Requirements
- Keep the class name Student.
- Store name and scores.
- Return 0.0 for an empty score array.
- Use the exact grade thresholds.
- Do not print.
ExamplesJAVACopy
new Student("Mina", new double[]{90,80,100}).calculateAverage();
Expected
TXTCopy
90.0
JAVACopy
new Student("Mina", new double[]{90,80,100}).getGrade();
Expected
TXTCopy
'A'
JAVACopy
new Student("Mina", new double[]{79,81}).getGrade();
Expected
TXTCopy
'B'
JAVACopy
new Student("Mina", new double[]{}).getGrade();
Expected
TXTCopy
'F'
Edge Cases
- An empty score array maps to average 0.0 and grade F.
- Exact threshold values belong to the higher grade.
- A single score is its own average.
Complexity Target
Average calculation should be O(n) for n scores.
Exercise .java
class Student {
private String name;
private double[] scores;
public Student(String name, double[] scores) {
this .name = name;
this .scores = scores;
}
public String getName() {
return name;
}
public double calculateAverage() {
// TODO
return 0.0;
}
public char getGrade() {
// TODO
return 'F';
}
}
SOLUTION — Exercise .java
class Student {
private String name;
private double[] scores;
public Student(String name, double[] scores) {
this .name = name;
this .scores = scores;
}
public String getName() {
return name;
}
public double calculateAverage() {
if (scores.length == 0) {
return 0.0;
}
double total = 0.0;
for (double score : scores) {
total += score;
}
return total / scores.length;
}
public char getGrade() {
double avg = calculateAverage();
if (avg >= 90) return 'A';
if (avg >= 80) return 'B';
if (avg >= 70) return 'C';
if (avg >= 60) return 'D';
return 'F';
}
}
EXPECTED AUTHOR TEST RESULT
Expected Result
All tests should pass with the Author Solution.
Expected
7 of 7 tests passed
RELATED LECTURES
Suggested Related Lecture Topics
- Object state with derived calculations
- Java classes and object-oriented design
9. HINTS
Hint 1 — Concept Reminder
Average is total divided by score count.
Hint 2 — Direction
Handle the empty array before division.
Hint 3 — Strong Hint
Check grade thresholds from highest to lowest.
SOLUTION EXPLANATION
Final Solution
class Student {
private String name;
private double[] scores;
public Student(String name, double[] scores) {
this .name = name;
this .scores = scores;
}
public String getName() {
return name;
}
public double calculateAverage() {
if (scores.length == 0) {
return 0.0;
}
double total = 0.0;
for (double score : scores) {
total += score;
}
return total / scores.length;
}
public char getGrade() {
double avg = calculateAverage();
if (avg >= 90) return 'A';
if (avg >= 80) return 'B';
if (avg >= 70) return 'C';
if (avg >= 60) return 'D';
return 'F';
}
}
How It Works
- The object stores name and scores.
- Average loops over scores and divides by length.
- The empty-array guard avoids division by zero.
- Grade compares the average against descending thresholds.
Example Walkthrough
Scores 90, 80, and 100 total 270. Dividing by 3 gives 90, so the grade is A.
Edge Cases
- An empty score array maps to average 0.0 and grade F.
- Exact threshold values belong to the higher grade.
- A single score is its own average.
Time Complexity
O(n) for average and grade.
Space Complexity
O(1) auxiliary space.
Common Mistakes
- Dividing by zero for empty scores.
- Using > instead of >= at boundaries.
- Checking grade thresholds in the wrong order.
- Losing decimal precision.
Course Coverage
The exercise collection covers
• Java Fundamentals
• Conditions and Switch Statements
• Loops, Methods, Numbers, and Recursion
• Arrays and Strings
• Object-Oriented Programming
• Collections Framework and Generics
• Exceptions, Regex, Date/Time, and File Handling
• Lambda Expressions and Stream API
• Multithreading and Concurrency
• Modern Java 21 Programming Features
This course is designed as independent Java practice material. The exercises are original learning activities created to help learners develop programming skills and are not copied from any live examination or assessment.
Who this course is for
Beginners who want structured Java coding practice after learning basic syntax.
Students preparing for Java programming interviews and coding assessments.
Developers who want to strengthen Java problem-solving skills.
Programmers revising Java fundamentals, OOP, collections, and modern Java features.
Learners looking for hands-on practice instead of only theoretical explanations.
Professionals refreshing their Java knowledge with practical coding challenges.
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