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Array problems in Java.md
Array problems in Java.md
 
 
Count Number of Bad Pairs: You are given a 0-indexed integer array nums. A pair of indices (i, j) is a bad pair if i < j and j - i != nums[j] - nums[i]. Return the total number of bad pairs in nums. Example 1: Input: nums = [4,1,3,3] Output: 5 Explanation: The pair (0, 1) is a bad pair since 1 - 0 != 1 - 4. The pair (0, 2) is a bad pair since 2 - 0 != 3 - 4, 2 != -1. The pair (0, 3) is a bad pair since 3 - 0 != 3 - 4, 3 != -1. The pair (1, 2) is a bad pair since 2 - 1 != 3 - 1, 1 != 2. The pair (2, 3) is a bad pair since 3 - 2 != 3 - 3, 1 != 0. There are a total of 5 bad pairs, so we return 5. Example 2: Input: nums = [1,2,3,4,5] Output: 0 Explanation: There are no bad pairs. Constraints: 1 <= nums.length <= 105 1 <= nums[i] <= 109.java.md
Count Number of Bad Pairs: You are given a 0-indexed integer array nums. A pair of indices (i, j) is a bad pair if i < j and j - i != nums[j] - nums[i]. Return the total number of bad pairs in nums. Example 1: Input: nums = [4,1,3,3] Output: 5 Explanation: The pair (0, 1) is a bad pair since 1 - 0 != 1 - 4. The pair (0, 2) is a bad pair since 2 - 0 != 3 - 4, 2 != -1. The pair (0, 3) is a bad pair since 3 - 0 != 3 - 4, 3 != -1. The pair (1, 2) is a bad pair since 2 - 1 != 3 - 1, 1 != 2. The pair (2, 3) is a bad pair since 3 - 2 != 3 - 3, 1 != 0. There are a total of 5 bad pairs, so we return 5. Example 2: Input: nums = [1,2,3,4,5] Output: 0 Explanation: There are no bad pairs. Constraints: 1 <= nums.length <= 105 1 <= nums[i] <= 109.java.md
 
 
Design a number container system that can do the following: Insert or Replace a number at the given index in the system. Return the smallest index for the given number in the system. Implement the NumberContainers class: NumberContainers() Initializes the number container system. void change(int index, int number) Fills the container at index with the number. If there is already a number at that index, replace it. int find(int number) Returns the smallest index for the given number, or -1 if there is no index that is filled by number in the system.md
Design a number container system that can do the following: Insert or Replace a number at the given index in the system. Return the smallest index for the given number in the system. Implement the NumberContainers class: NumberContainers() Initializes the number container system. void change(int index, int number) Fills the container at index with the number. If there is already a number at that index, replace it. int find(int number) Returns the smallest index for the given number, or -1 if there is no index that is filled by number in the system.md
 
 
Distinct Ball Colors Query.md
Distinct Ball Colors Query.md
 
 
Find the Number of Distinct Colors Among the Balls.java
Find the Number of Distinct Colors Among the Balls.java
 
 
Find the Punishment Number of an Integer.md
Find the Punishment Number of an Integer.md
 
 
Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order. Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Explanation: Because nums[0] + nums[1] == 9, we return [0, 1]. Example 2: Input: nums = [3,2,4], target = 6 Output: [1,2] Example 3: Input: nums = [3,3], target = 6 Output: [0,1] Constraints: 2 <= nums.length <= 104 -109 <= nums[i] <= 109 -109 <= target <= 109 Only one valid answer exists.java
Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order. Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Explanation: Because nums[0] + nums[1] == 9, we return [0, 1]. Example 2: Input: nums = [3,2,4], target = 6 Output: [1,2] Example 3: Input: nums = [3,3], target = 6 Output: [0,1] Constraints: 2 <= nums.length <= 104 -109 <= nums[i] <= 109 -109 <= target <= 109 Only one valid answer exists.java
 
 
HashMap.md
HashMap.md
 
 
JavaDevelopmentResources.md
JavaDevelopmentResources.md
 
 
List, Set, Map, Queue, Stack, Iterator.md
List, Set, Map, Queue, Stack, Iterator.md
 
 
README.md
README.md
 
 
Tuple with Same Product: Given an array nums of distinct positive integers, return the number of tuples (a, b, c, d) such that a * b = c * d where a, b, c, and d are elements of nums, and a != b != c != d. Example 1: Input: nums = [2,3,4,6] Output: 8 Explanation: There are 8 valid tuples: (2,6,3,4) , (2,6,4,3) , (6,2,3,4) , (6,2,4,3) (3,4,2,6) , (4,3,2,6) , (3,4,6,2) , (4,3,6,2) Example 2: Input: nums = [1,2,4,5,10] Output: 16 Explanation: There are 16 valid tuples: (1,10,2,5) , (1,10,5,2) , (10,1,2,5) , (10,1,5,2) (2,5,1,10) , (2,5,10,1) , (5,2,1,10) , (5,2,10,1) (2,10,4,5) , (2,10,5,4) , (10,2,4,5) , (10,2,5,4) (4,5,2,10) , (4,5,10,2) , (5,4,2,10) , (5,4,10,2) Constraints: 1 <= nums.length <= 1000 1 <= nums[i] <= 104 All elements in nums are distinct.java
Tuple with Same Product: Given an array nums of distinct positive integers, return the number of tuples (a, b, c, d) such that a * b = c * d where a, b, c, and d are elements of nums, and a != b != c != d. Example 1: Input: nums = [2,3,4,6] Output: 8 Explanation: There are 8 valid tuples: (2,6,3,4) , (2,6,4,3) , (6,2,3,4) , (6,2,4,3) (3,4,2,6) , (4,3,2,6) , (3,4,6,2) , (4,3,6,2) Example 2: Input: nums = [1,2,4,5,10] Output: 16 Explanation: There are 16 valid tuples: (1,10,2,5) , (1,10,5,2) , (10,1,2,5) , (10,1,5,2) (2,5,1,10) , (2,5,10,1) , (5,2,1,10) , (5,2,10,1) (2,10,4,5) , (2,10,5,4) , (10,2,4,5) , (10,2,5,4) (4,5,2,10) , (4,5,10,2) , (5,4,2,10) , (5,4,10,2) Constraints: 1 <= nums.length <= 1000 1 <= nums[i] <= 104 All elements in nums are distinct.java
 
 

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javaDeveloper-Roadmap

Here's a structured Java Developer Roadmap to guide your learning journey:

1. Core Java (Beginner Level)

✅ Basic Syntax – Variables, Data Types, Operators, Loops, Conditionals
✅ OOP Concepts – Classes, Objects, Inheritance, Polymorphism, Abstraction, Encapsulation
✅ Exception Handling – Try-Catch, Throws, Custom Exceptions
✅ Collections Framework – List, Set, Map, Queue, Stack, Iterator
✅ Multithreading & Concurrency – Threads, Synchronization, Executors
✅ File Handling (I/O) – Reading/Writing Files, Serialization
✅ JVM, JDK, JRE & Garbage Collection

🛠 Practice: Solve problems on LeetCode, HackerRank, or CodeWars.

2. Advanced Java (Intermediate Level)

✅ Java 8+ Features – Streams, Lambda Expressions, Functional Interfaces, Optional, Method References
✅ Concurrency Utilities – CompletableFuture, ForkJoinPool
✅ JDBC (Database Connectivity) – CRUD Operations, Connection Pooling
✅ Networking (Sockets, HTTP Requests)
✅ Logging Frameworks – Log4j, SLF4J
✅ Unit Testing – JUnit, Mockito

🛠 Projects: Build CRUD applications using JDBC & Java 8 features.

3. Spring Framework (Backend Development)

✅ Spring Core – Dependency Injection, Beans, Annotations
✅ Spring Boot – REST APIs, Microservices, Spring Data JPA
✅ Spring Security – JWT Authentication, OAuth2
✅ Spring MVC – Model-View-Controller architecture
✅ Spring Cloud – Eureka, Feign, Resilience4J, Config Server
✅ Spring Batch & Spring Kafka

🛠 Projects: Build a REST API using Spring Boot and connect it to a database.

4. Database Management & SQL

✅ SQL Basics – Joins, Indexes, Views, Stored Procedures
✅ RDBMS – MySQL, PostgreSQL, Oracle
✅ NoSQL Databases – MongoDB, Redis, Cassandra
✅ ORM (Object-Relational Mapping) – Hibernate, JPA
✅ Database Optimization – Query Optimization, Indexing

🛠 Projects: Build a full-stack app using Spring Boot + MySQL/PostgreSQL.

5. Tools & Build Systems

✅ Maven & Gradle – Dependency Management
✅ Docker – Containerization
✅ Kubernetes – Orchestration
✅ CI/CD – Jenkins, GitHub Actions
✅ Version Control – Git, GitHub, GitLab

🛠 Projects: Create a Spring Boot Dockerized App with GitHub Actions for CI/CD.

6. Microservices & Cloud Deployment

✅ Microservices Architecture – API Gateway, Service Discovery, Load Balancing
✅ Event-Driven Architecture – RabbitMQ, Kafka
✅ Cloud Platforms – AWS (EC2, S3, Lambda, RDS), Azure, GCP
✅ Serverless Computing – AWS Lambda, Google Cloud Functions

🛠 Projects: Deploy a Spring Boot Microservice to AWS/GCP.

7. Frontend (Optional but Useful)

✅ HTML, CSS, JavaScript
✅ Frontend Frameworks – React, Angular
✅ Integration with Java Backend – REST APIs, GraphQL

🛠 Projects: Build a full-stack Java web application with React + Spring Boot.

8. System Design & Advanced Concepts

✅ Design Patterns – Singleton, Factory, Observer, Builder
✅ Distributed Systems – CAP Theorem, Consistency Models, Caching Strategies
✅ Performance Optimization – Profiling, Memory Management
✅ Security Best Practices – OWASP, HTTPS, CSRF, CORS

🛠 Projects: Design highly scalable systems using Java & distributed computing.

Next Steps

🔹 Open Source Contributions – Contribute to Java repositories on GitHub.
🔹 Competitive Coding – Participate in Codeforces, LeetCode, TopCoder.
🔹 Certifications – Oracle Certified Java Programmer (OCP), AWS Certified Developer.
🔹 Internships & Job Applications – Showcase projects, build a strong GitHub profile.

Since you want to be a Java developer, this roadmap aligns with your goal. Let me know if you want a detailed plan for any section! 🚀

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