Learning Abstraction in Java: ATM Example

🚀 Day 24 of Learning Java Full Stack Development – Multithreading Life Cycle & States in Java 🧩 What is a Thread Life Cycle? A thread life cycle represents the complete journey of a thread — from the moment it is created, to the point it finishes its task and dies. Java defines several states that a thread can be in at any given time, managed automatically by the JVM (Java Virtual Machine). 👉 By understanding these states, you can build efficient, responsive, and well-synchronized multithreaded applications. 🌀 Thread Life Cycle States in Java Java defines five major thread states as part of its life cycle: 1️⃣ New (Born State): The thread is created but not yet started. 2️⃣ Runnable (Ready to Run): The thread is ready to run and waiting for CPU time. 3️⃣ Running (Active State): The thread is executing its run() method. 4️⃣ Blocked / Waiting (Paused State): A thread enters the waiting state when it becomes temporarily inactive using methods like sleep(), wait(), or join(), while waiting for another thread to finish or release a resource. 5️⃣ Terminated (Dead State): Once the run() method finishes execution or the thread is stopped, it enters the terminated state. 🔁 State Transitions Simplified Here’s how threads typically move between states: New → start() → Runnable → Running → Waiting/Blocked → Runnable → Terminated 💻 Complete Example: class MyThread extends Thread { public void run() { System.out.println("Thread is running..."); try { Thread.sleep(2000); // Thread enters waiting state } catch (InterruptedException e) { System.out.println("Thread interrupted..."); } System.out.println("Thread has finished execution."); } } public class ThreadLifeCycleExample { public static void main(String[] args) { MyThread t = new MyThread(); // New System.out.println("Thread State after creation: " + t.getState()); t.start(); // Runnable → Running System.out.println("Thread State after start: " + t.getState()); } } ✅ Output Thread State after creation: NEW Thread State after start: RUNNABLE Thread is running... Thread has finished execution. 🌟 Today’s key lesson: mastering concurrency is about writing faster and more reliable code while maintaining control over execution flow. Java’s multithreading model simplifies this powerfully yet elegantly. 🔜 Excited to continue exploring synchronization next! #Day24 #JavaLearning #Multithreading #ThreadLifeCycle #FullStackDevelopment #JavaDeveloper #JavaThreads #ProgrammingJourney #LearningEveryday #SoftwareEngineer #BackendDevelopment #Concurrency #JavaFundamentals #TechLearning #DevelopersJourney #JavaCommunity #CodingPractice #ThreadManagement #JavaSkills #JavaProgramming #DailyLExample

🚀 Java Learning Series — Day 3 Topic: Exception and Its Types ☕ When we write a program, things don’t always go as planned Right??? Java gives us "Exceptions" — Special ways to handle those unexpected Bugs so our code doesn’t crash suddenly. ------------------------------------- 💡 Definition: An Exception is like a signal that something went wrong during program execution. Instead of stopping everything, Java lets us catch and handle it. ------------------------------------- ✅ Dont miss to read the Interview questions from this Topic in the end 💀😋 ------------------------------------- 🧩 Types of Exceptions: 1. CHECKED EXCEPTIONS → Problems Java expects you to handle before running (e.g., reading a missing file). ----Must fix---- 2. UNCHECKED EXCEPTIONS → Problems that happen while running (e.g., dividing by zero). 3. ERRORS (Bugs) → Serious system-level problems (e.g., memory full, system crash). ------------------------------------- 🧠 Simple Example: class ExceptionTypesStory { public static void main(String[] args) { try { int apples = 5; int kids = 0; int eachGets = apples / kids; // Oops! Unchecked exception System.out.println("Each kid gets: " + eachGets); } catch (ArithmeticException e) { System.out.println("Oops! Can't divide apples by zero kids."); } //See here how I handled the error 👇🏃 try { Thread.sleep(500); // Checked exception } catch (InterruptedException e) { System.out.println("Someone woke me up too early!"); } System.out.println("###_Story_over_###"); //Everything handled 😜smoothly } } ------------------------------------- ⚙️ Real-World Connections: 1. Online Shopping App– Item goes out of stock → Exception handled, shows “Out of Stock” instead of crashing. 2. Bank App – Network drops during payment → Checked exception, retried safely. 3. Music Player – Song file missing → Checked exception handled, plays next song. 5. Web Browser – Out of memory loading heavy tabs → Error, can’t recover easily. ------------------------------------- 🔥 Interview-Style Quick Questions — Exceptions in Java 1️⃣ What is the difference between Checked and Unchecked Exceptions? 2️⃣ Can we handle Errors using try-catch? If not, why? 3️⃣ Is it mandatory to handle Checked Exceptions? 4️⃣ What happens if you don’t handle an Unchecked Exception? 5️⃣ Can a single catch block handle multiple exceptions? 6️⃣ What is the parent class of all exceptions in Java? 7️⃣ What happens if you put finally block before catch? 8️⃣ Can we have a try block without catch? 9️⃣ What’s the difference between throw and throws in exception context? 🔟 Why is Exception Handling important in large-scale applications? #Java #100DaysOfJava #CodingJourney #ExceptionHandling #SoftwareEngineer #SoftwareEngineering #LearningNeverStops #MERNtoJavaJourney

💻 Day 11 of My Java Learning Journey 💯 ~ Understanding Short-Circuit Operators in Java (&& and ||) Today, I explored an important concept in Java: Short-Circuit Operators — && (AND) and || (OR). These operators help in making conditional statements more efficient by controlling how expressions are evaluated. 🔹 What Are Short-Circuit Operators? Short-circuiting means that Java stops evaluating further conditions once the result is determined. && (AND Operator): → If the first condition is false, the second condition is not evaluated. → Used when both conditions must be true. || (OR Operator): → If the first condition is true, the second condition is not evaluated. → Used when only one condition needs to be true. 🧩 Code Example -------------------------------------code start-------------------------------------- public class ShortCircuitDemo { public static void main(String[] args) { // && operator examples int x = 15, y = 12; if (--x >= 14 && --y <= 12) { --x; } else { --y; } System.out.println("x = " + x + " y = " + y); int p = 15, q = 12; if (--p >= 15 && --q <= 10) { --p; } else { --q; } System.out.println("p = " + p + " q = " + q); // || operator examples int a = 10, b = 5; if (++a >= 10 || ++b <= 5) { ++a; } else { ++b; } System.out.println("a = " + a + " b = " + b); int n = 8, m = 3; if (++n >= 10 || ++m <= 2) { ++n; } else { ++m; } System.out.println("n = " + n + " m = " + m); } } -------------------------------------code output-------------------------------------- x = 13 y = 11 p = 14 q = 11 a = 12 b = 5 n = 9 m = 4 -------------------------------------code end-------------------------------------- 💡 Key Takeaways && → If the first condition is false, the second is skipped. || → If the first condition is true, the second is skipped. Helps in optimizing code execution and avoiding unnecessary evaluations. Learning these small but impactful details helps me write smarter and more efficient Java code every day. 🚀 #Day11 #JavaLearning #ShortCircuitOperators #LogicalOperators #100DaysOfCode #JavaDevelopment #ProgrammingConcepts #DevOps #CodingJourney #YuviLearnsJava

🌟 Day 14 of My Java Learning Journey 🔥 💯 Hey everyone! 👋 ~ Today’s topic was all about decision-making in Java — how a program chooses which path to follow based on given conditions. 💡 . I explored how to find the greatest number among multiple values using nested if-else statements, one of the core parts of selection statements in Java. 💻 Here’s the code I worked on today: 👇 -------------------------------------code start-------------------------------------- public class FindGreaterNumberDemo2 { public static void main(String[] args) { int p = 11; int q = 22; int r = 33; int s = 44; if (p > r && p > s && p > q) { System.out.println("p is greater number "); } else if (q > s && q > p && q > r) { System.out.println("q is greater number"); } else if (r > p && r > s && r > q) { System.out.println("r is greater number"); } else { System.out.println("s is greater number"); } } } -------------------------------------code output------------------------------------ s is greater number ---------------------------------------code end-------------------------------------- . 🔍 Explanation: We have four integer variables: p, q, r, and s. Using an if-else-if ladder, we compare each number with the others using the logical AND (&&) operator. The first condition that turns out true will print which number is the greatest. If none of them match, the else block executes, showing that s is the greatest. . 💡 Key Takeaway: Selection statements like if, else if, and else help control the program’s logic — deciding what happens next depending on the condition. . 🚀 What’s next? In the upcoming posts, I’ll share many more real-world examples related to selection statements, so we can deeply understand how decision-making works in Java programs. Stay tuned — it’s gonna get crazy cool and more practical! 💻🔥 . #Java #100DaysOfCode #Day14 #JavaLearningJourney #FlowControl #IfElse #SelectionStatements #DevOps #Programming #CodingJourney #LearnJava #TechLearner #CodeNewbie .

🔜 🚀 Day 13 of Learning java 💡 OOPs Concepts in Java Object-Oriented Programming (OOPs) is the foundation of Java. It helps us write cleaner, modular, and reusable code. 🧩 Here are the 4 main pillars of OOPs 👇 ✨ Why OOPs? ✅ Better code reusability ✅ Improved security ✅ Easier maintenance ✅ Real-world modeling 1. 🔒 Encapsulation Encapsulation means wrapping data (variables) and methods (functions) that operate on that data into a single unit — called a class. It’s like putting data and behavior inside a capsule 💊 to protect it from outside interference. Key idea: Data is hidden using private variables. Access is given through public getter and setter methods. Example: class Account { private double balance; // data hidden // getter method public double getBalance() { return balance; } // setter method public void setBalance(double balance) { if (balance > 0) this.balance = balance; } } Benefits: ✅ Data protection ✅ Controlled access ✅ Improved code security 2. 🧬 Inheritance Inheritance allows one class to inherit the properties (fields) and behaviors (methods) of another class. This helps promote code reusability and establish a parent-child relationship between classes. Syntax: class ChildClass extends ParentClass { } Example: class Animal { void eat() { System.out.println("Eating..."); } } class Dog extends Animal { void bark() { System.out.println("Barking..."); } } Explanation: Dog inherits eat() from Animal. You can now reuse code instead of writing it again. Benefits: ✅ Code reuse ✅ Easier maintenance ✅ Logical class hierarchy 3. 🎭 Polymorphism Polymorphism means “many forms.” It allows methods to behave differently based on the object that’s calling them. There are two types: Compile-time Polymorphism (Method Overloading) Runtime Polymorphism (Method Overriding) Example of Overriding (Runtime Polymorphism): class Shape { void draw() { System.out.println("Drawing a shape"); } } class Circle extends Shape { void draw() { System.out.println("Drawing a circle"); } } Output: Drawing a circle Explanation: Even though both classes have draw(), the method in the child class is executed at runtime. Benefits: ✅ Flexibility in code ✅ Easy to extend functionality ✅ Supports dynamic behavior 4. 👻 Abstraction Abstraction means hiding complex implementation details and showing only what’s necessary. It focuses on what an object does instead of how it does it. In Java, abstraction is achieved through: Abstract classes (abstract keyword) Interfaces Example: abstract class Animal { abstract void sound(); // abstract } class Dog extends Animal { void sound() { System.out.println("Barks"); } } Explanation: The abstract class Animal defines a concept (sound()), But the subclass Dog provides the specific implementation. Benefits: ✅ Reduces complexity ✅ Increases flexibility

🚀 Day 23 | Learning Java Full Stack Development: Multithreading in Java 🧵 Multithreading in Java is a process of executing two or more threads simultaneously to achieve concurrent execution of tasks. It improves application performance by efficiently utilizing CPU resources. Each thread runs independently while sharing the same memory, making programs faster and more responsive, especially for complex or long-running tasks. In a system, the OS handles multiple tasks sequentially or concurrently — a concept called Multitasking, divided into two types. 👇 1️⃣ Process-Based Multitasking Process-based multitasking, also known as heavyweight processing, allows multiple programs to run simultaneously, each with its own memory and resources — for example, using Word, a browser, and a music player at the same time. 2️⃣ Thread-Based Multitasking Here, multiple tasks (threads) run within a single process, sharing the same memory and resources. This makes it more efficient and lightweight — hence known as Lightweight Processing. 👉 Thread: A thread represents an independent execution path, allowing Java to run multiple threads concurrently for better performance. 🏗️ How to Create a Thread in Java: ➠ There are two main ways to create threads in Java 1️⃣ By extending Thread class class MyThread extends Thread { public void run() { // thread logic here } } public class Main { public static void main(String[] args) { MyThread t = new MyThread(); t.start(); // starts the thread } } 2️⃣ By Implementing the Runnable Interface class MyRunnable implements Runnable { public void run() { System.out.println("Runnable thread is running..."); } } public class Main { public static void main(String[] args) { Thread t = new Thread(new MyRunnable()); t.start(); } } 👉 Remember: Calling start() automatically invokes the run() method in a new thread, while calling run() directly executes it in the main thread. ⚙️Thread Operations and Methods Threads can be controlled, paused, or prioritized using built-in methods in the Thread class. 1. sleep(long millis) : Temporarily pauses the thread for a specified time (in milliseconds). 2. join(): Ensures one thread waits for another to complete before continuing. 3. setPriority(int newPriority): Sets the priority of a thread between 1 (lowest) and 10 (highest). ● Thread.MIN_PRIORITY (1) ● Thread.NORM_PRIORITY (5 - default) ● Thread.MAX_PRIORITY (10) 👉 Threads with higher priority are scheduled before lower-priority threads. 4. setDaemon(true): Converts a user thread into a daemon thread (a background or service thread). 💼 Thread Groups: In Java, a Thread Group is a way to organize and manage multiple threads together as a single unit. 🔜 Next Up : Thread Lifecycle & States in Java #Day22 #JavaLearningJourney #Multithreading #JavaThreads #FullStackDevelopment #JavaProgramming #BackendDevelopment #Concurrency #Threading #CodingCommunity #JavaDeveloper #LearningInPublic #CodeEveryday #SoftwareEngineering

🎯 Day 15 of My Java Learning Journey 🎯 . Hey everyone! 👋 .. Today I explored Selection Statements again — but this time, I focused on finding the smallest number among four values using if-else if ladder in Java. Here’s the code I wrote 👇 --------------------------------------code start--------------------------------------- public class FindSmallerNumberDemo2 { public static void main(String[] args) { int l = 1; int m = 2; int n = 3; int o = 4; if (l < m && l < n && l < o) { System.out.println("l is smaller"); } else if (m < o && m < n && m < l) { System.out.println("m is smaller"); } else if (o < n && o < m && o < l) { System.out.println("o is smaller"); } else { System.out.println("n is smaller"); } } } --------------------------------------code output---------------------------------- l is smaller number -------------------------------------code end--------------------------------------- . 💡 Explanation: I’ve declared four integer variables — l, m, n, and o. The if statement checks multiple conditions using logical AND (&&) to make sure one number is smaller than all others. . If the first condition fails, the program moves to the next else if condition. Finally, if none of the earlier conditions are true, the else block executes — meaning the last variable n is the smallest. . 🧠 This program is a simple way to understand how comparison and logical operators work together in decision-making statements. In the next few posts, I’ll share more concepts related to selection and looping statements in Java 🚀 . #Day15 #JavaLearningJourney #100DaysOfCode #LearnJava #Programming #DevOps #Coding #JavaBeginners #SelectionStatement #IfElseInJava .

🚀 Day 15 of Learning Java Full Stack Development — Abstract Classes & Abstract Methods in Java 👋 Hello Everyone! Today marks another exciting milestone in my Java learning journey! I explored one of the most important concepts in Object-Oriented Programming (OOP) — Abstract Classes & Abstract Methods in Java. ➤ Abstract Class: An abstract class in Java is a special type of class that is declared using the abstract keyword. In Java, a class is called an abstract class if it contains at least one abstract method. ➤ Abstract Method: An abstract method is a method that is declared without a body — meaning it only contains the method name and signature, but no implementation. It is defined using the abstract keyword and must be declared inside an abstract class or an interface. 👉 Simply put, an abstract class acts as a blueprint for its subclasses. It defines what needs to be done, but leaves the “how” part to the subclasses that extend it. ✅ Example: abstract class Example { void display() { // concrete method System.out.println("Hello"); } abstract void show(); // abstract method } In the above example: ● display() is a concrete method because it contains an implementation. ● show() is an abstract method because it has no body. ● Since the class contains at least one abstract method, it becomes an abstract class. 👉 Note : An abstract class cannot be instantiated directly” means that you cannot create an object of an abstract class using the new keyword. Instead, you must inherit it in a subclass and then create an object of that subclass. ✅Example: abstract class Vehicle { abstract void start(); // Abstract method (no body) void stop() { // Concrete method System.out.println("Vehicle stopped."); } } class Car extends Vehicle { void start() { System.out.println("Car started with a key."); } } public class Main { public static void main(String[] args) { // Vehicle v = new Vehicle(); ❌ Not allowed Car car = new Car(); // ✅ Allowed car.start(); car.stop(); } } 🌟Key Takeaways ✔️ An abstract method is declared without a method body. ✔️ An abstract class can have both abstract and concrete methods (methods with definitions). ✔️ Subclasses must implement all abstract methods. ✔️ Objects cannot be created directly for abstract classes. 🔥 Abstract classes help make Java programs more organized, easier to maintain, and more scalable by promoting clean code and proper object-oriented design. I’m one step closer to mastering the OOP concepts that form the foundation of Java Full Stack Development. #Java #OOPsConcepts #AbstractClass #Inheritance #Encapsulation #LearningJourney #JavaDeveloper #BackendDevelopment #JavaFullStackDevelopment #FullStackDeveloper #JavaProgramming #Day15 #LearningNeverStops #SoftwareEngineering #LearnJava #JavaDeveloper #CleanCode #ProgrammingConcepts

#DAY69 #100DaysOfCode #JavaFullStackDevelopment Journey Hello LinkedIn family! Day 69 of My Java Learning Journey – Deque and Its Methods in Java Today on Day 69, I explored one of the most flexible data structures in Java — the Deque (Double-Ended Queue). A Deque allows insertion and deletion from both ends, which makes it more powerful than a normal queue or stack. It is part of the java.util package and is commonly implemented using ArrayDeque or LinkedList. -> Why Deque Is Unique Deque can act as: Queue → add at rear, remove from front Stack → add at front, remove from front Bidirectional structure → operations on both ends Because of this, Deque is used in: ✔ Sliding window algorithms ✔ Backtracking ✔ Expression evaluation ✔ Undo/Redo actions ✔ Browser history navigation -> Important Deque Methods in Java Java provides clear categories of methods under the Deque interface. 1️⃣ Insertion Methods Front: addFirst(E e) → inserts at head offerFirst(E e) → safe insert Rear: addLast(E e) → inserts at tail offerLast(E e) → safe insert 2️⃣ Removal Methods Front: removeFirst() → removes head pollFirst() → safe remove Rear: removeLast() → removes tail pollLast() → safe remove 3️⃣ Retrieval Methods (Peek) Front Peek: getFirst() peekFirst() Rear Peek: getLast() peekLast() Peeking helps check elements without removing them. 4️⃣ Stack-Like Methods Deque can completely replace the outdated Stack class: push(E e) → add to the front pop() → remove from the front peek() → get top element This makes Deque faster and more efficient. ->Why Deque Stands Out Today I learned how a single structure can support both queue and stack behavior with high efficiency. Its methods make it ideal for algorithms that require quick access from both ends. Deque plays a major role in solving modern coding problems due to its speed and flexibility. ->Conclusion Deque may look simple, but it provides powerful control over how data is added, removed, and accessed. This topic gave me more clarity on real-world applications like BFS, undo-redo actions, and sliding window problems. A big thanks to my mentor Gurugubelli Vijaya Kumar Sir and the 10000 Coders institute for constantly guiding me and helping me build a strong foundation in programming concepts. #100DaysOfCode #JavaLearning #JavaDeveloper #Deque #CollectionsFramework #DataStructures #JavaProgramming #CodingJourney #LearnJava #ProgrammersLife #TechJourney #CodeEveryday

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