8. Modern Java, Coding Practice & Interview Question Bank
Chapters 30-31 + Interview Bank: Java Records, Enums, SOLID Principles, Coding Practice Problems & 30+ Final Interview Question Bank
Module 1: Modern Java: Records, Enums & SOLID Design Principles
Writing concise data carriers with Records, typed Enums, and maintainable SOLID architecture.
🇬🇧 English Definition
Java Records (record Student(int id, String name) {}) create immutable data carriers reducing boilerplate. SOLID principles (SRP, OCP, LSP, ISP, DIP) guide object-oriented software design.
🇮🇳 Hinglish Definition
Record concise DTO data holder class banata hai. SOLID 5 design principles hain jo code ko scalable aur maintainable banate hain.
Core Concepts & Rules
- Records: Automatically generates constructors, getters, equals(), hashCode(), and toString().
- SOLID Principles: Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion.
🔍 Line-by-Line Code Breakdown
- Line 1: record Student(int id, String name) {} defines concise record type.
- Line 4: s.name() accesses generated record getter method.
🎯 Interview Focus & Questions
- Q: What is a Java Record?
A: A concise immutable data-carrier class with automatically generated accessors, equals(), hashCode(), and toString(). - Q: What is SOLID?
A: Five OO design principles: Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion.
public class ModernJavaDemo {
record Student(int id, String name) {}
enum Status { PENDING, APPROVED, REJECTED }
public static void main(String[] args) {
Student s = new Student(101, "Aman");
System.out.println("Record Student: " + s.name() + " | Status: " + Status.APPROVED);
}
}Module 2: Java Coding Practice Programs & Final Interview Question Bank
Essential coding interview algorithms (Prime, Reverse, Palindrome, HashMap Frequency) and technical Q&A bank.
🇬🇧 English Definition
Hands-on coding algorithms: Prime verification, Number reversing, Palindrome checking, and Character frequency mapping with HashMap. Includes full 30+ Technical Interview Question Bank.
🇮🇳 Hinglish Definition
Coding interview me frequency count, palindrome aur prime algorithms frequently pooche jate hain. Comprehensive Interview Question Bank rapid revision me help karta hai.
Core Concepts & Rules
- Prime Check: Check divisors up to sqrt(n).
- HashMap Frequency: map.merge(c, 1, Integer::sum) counts character occurrences cleanly.
- Palindrome Check: Compare original string with reversed StringBuilder.
🔍 Line-by-Line Code Breakdown
- Line 1-5: Character frequency mapping using HashMap and map.merge().
- Line 7-9: Palindrome checking comparing string with reversed StringBuilder.
🎯 Interview Focus & Questions
- Q: HashMap vs TreeMap?
A: HashMap is hash-based with O(1) average lookup; TreeMap keeps keys sorted with O(log N) operations. - Q: What is the coding interview formula?
A: Clarify input/output -> Explain approach -> Choose data structure -> Write code -> Test edge cases -> Explain complexity.
import java.util.*;
public class PracticeCodingDemo {
public static void main(String[] args) {
// 1. Character Frequency with HashMap
Map<Character, Integer> freq = new HashMap<>();
for (char c : "banana".toCharArray()) {
freq.merge(c, 1, Integer::sum);
}
System.out.println("Character Frequencies: " + freq);
// 2. Palindrome Check
String str = "madam";
boolean isPalindrome = str.equals(new StringBuilder(str).reverse().toString());
System.out.println("Is '" + str + "' Palindrome? " + isPalindrome);
}
}