📚 Java Examples & Blockchain Implementation

A collection of Java tutorials, examples, and exercises covering core Java concepts and blockchain implementation.

📖 Table of Contents

• Collections & Type Casting
• Blockchain Implementation
• Project History

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🔄 Collections & Type Casting

Casting Type

Learn about type safety and unchecked casting in Java:

• Type Safety & Unchecked Cast from Object to Hashtable

Collections

• List Documentation

Nested Collections & HashTable

Explore collections with the HashTable class implementation:

import java.util.Hashtable;

class HashTable {
    public static void main(String[] arg) {
        // Creating a hash table
        Hashtable<Integer, String> h = new Hashtable<Integer, String>();

        h.put(3, "Geeks");
        h.put(2, "forGeeks");
        h.put(1, "isBest");
        h.put(4, "Quamm");
        h.put(5, "Qq");
        h.put(6, "Qq");

        // Create a clone or shallow copy of hash table h
        Hashtable<Integer, String> h1 = (Hashtable<Integer, String>) h.clone();
        Hashtable<Integer, String> h2 = (Hashtable<Integer, String>) h1.clone();

        System.out.println("-- start --");
        System.out.println(">h: " + h);
        System.out.println("clone h->h1: " + h1);

        // Clear hash table h
        h.clear();

        // Checking hash table h
        System.out.println("after clearing h: " + h);
        System.out.println(">h1: " + h1);
        System.out.println(">h2: " + h2);

        // Proper way to create a clone of hash table
        Hashtable<?, ?> h3 = (Hashtable<?, ?>) h.clone();
        System.out.println(">(String) h3: " + h3);
    }
}

Key Classes:

• 📁 HashTable.java - Hashtable implementation examples
• 📁 Vehicle.java - Vehicle class hierarchy examples
• 📁 CollectionsEx1.java - Nested collections examples
• 📁 OptionalBasicExample.java - Optional API examples

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⛓️ Blockchain Implementation

A simple blockchain implementation built with Java, based on industry best practices and detailed articles.

Resources

• 📖 Create Simple Blockchain in Java Tutorial
• 📖 Blockchain Implementation in Java

Core Components

• Block.java 🧱 - Represents individual blocks in the blockchain chain
• NoobChain.java ⛓️ - Basic blockchain implementation
• NoobChainV2.java ⛓️ - Enhanced blockchain with transactions
• StringUtil.java 🔧 - Utility functions for blockchain operations
• Transaction.java 💰 - Transaction handling
• TransactionInput.java 📥 - Transaction input management
• TransactionOutput.java 📤 - Transaction output management
• Wallet.java 💳 - Wallet functionality for blockchain

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📋 Project History

Date	Event
2019-11-03	Added Gradle configuration for log4j2 JAR generation
2019-11-06	Added blockchain package
2020-02-14	Updated README.md documentation

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🚀 Getting Started

# Build the project
./gradlew build

# Run tests
./gradlew test

📝 License & Attribution

This project contains examples and tutorials referenced from various sources including Medium and UltimaSolution blog posts.