Java Tutorial Index

Java Tutorial Java Features C++ vs Java Java History Java Hello World Java Development Kit Java Runtime Environment Java Virtual Machine Difference between JDK, JRE, and JVM Memory Areas in Java Java Operators Java Keywords Primitive Data Types Variables

Java Loops

Java Do While Loop Java While Loop Java For Loop Java Enhanced For Loop

Java Programs

Java Basic Programs Factorial Program in Java Fibonacci Series Program in Java Prime Number Program in Java Palindrome Number Program in Java Armstrong Number Program in Java Anagram Program in Java Pattern Programs in Java Calculator Program in Java Leap Year Program in Java Addition Program in Java Number Pattern Programs in Java Star Pattern Programs in Java Package Program in Java Pyramid Program in Java Sorting Program in Java String Palindrome Program in Java Even Odd Program in Java For Loop Program in Java If Else Program in Java Switch Case Program in Java GCD Program in Java LCM Program in Java Hello Program in Java Matrix Program in Java Menu Driven Program in Java Series Program in Java Client Server Program in Java Swapping Program in Java Pig Latin Program in Java Tower of Hanoi Program in Java Recursion Program in Java Matrix Multiplication Program in Java Perfect Number Program in Java Classes and Objects in Java Example Programs String Programs in Java Array Programs in Java Constructor Program in Java Inheritance Program in Java Abstract class Program in Java Interface Program in Java Encapsulation Program in Java Polymorphism Program in Java Exception Handling Program in Java Multithreading Program in Java Thread Program in Java Collection Programs in Java ArrayList Program in Java Stack Program in Java Applet Program in Java Swing Program in Java JDBC Program in Java How to run Java program in command prompt How to run Java program in Eclipse Program to find and replace characters on string in java Program to find the duplicate characters in a string Program to check whether a given character is present in a string or not Java Program to Print Permutations of String Java program to find frequency of characters in a string Java Program to remove duplicate characters in a string

Java Sorting

Sorting Algorithms in Java Merge Sort in Java Quick Sort in Java Bubble Sort in Java Insertion Sort in Java Selection Sort in Java Heap Sort in Java Radix Sort in Java Topological Sort in Java Bucket Sort in Java Counting Sort in Java

Java OOPs Concepts

OOPs - Object Oriented Programming Objects and Classes in Java Methods in Java Java Naming Conventions Constructors in Java Java this keyword Java static keyword Inheritance in Java Aggregation in Java Java super keyword Constructor Chaining and Constructor Overloading Java Polymorphism Static and Dynamic Binding in Java Java Abstraction Abstract class in Java Interface in Java Difference between Abstract class and Interface Java final keyword Packages in Java Access Modifiers in Java Java Wrapper classes Java Numbers Java Characters Java Integer Java Boolean Java Arrays Java Command Line Arguments Java strictfp Keyword Java Math

Java Strings

Java Strings Java String Methods StringBuilder in Java StringBuffer in Java Java Regular Expressions StringBuffer vs StringBuilder String vs StringBuffer String vs StringBuilder String Manipulation in Java Java String Concatenation How to Reverse a String in Java String Array in Java How to Compare Two Strings in Java How to Concatenate Two Strings in Java Why String in Immutable in Java java.lang.NumberFormatException for Input String String Pool in Java Java Generate Random String How to take String Input in Java Java String Interview Questions

Java Exceptions

Exception Handling in Java Java try catch Java throw Java throws Difference between throw and throws Java finally Java Custom Exception Java Exception Propagation

Garbage Collection

Automatic Resource Management in Java Java Garbage Collection Java finalize() Java gc() Difference between final, finally and finalize

Multithreading

Multithreading in Java Process and Thread in Java Basic Terms in Multithreading Java Thread creation Thread Scheduler in Java Java Thread class DeadLock in Java

Java IO

Java IO Java Read File Java file Reader Java Buffer Reader Java file Writer Java BufferedWriter Java InputStreamReader Scanner in Java Java StringReader Java StringReader Class Java StringWriter Class Java PrintWriter Java File Java Read File Line By Line Java FileInputStream Java FileOutputStream Java Create File Java Delete File Java Open File Java Read File to String Java copy file Jar File in Java Java FileNotFoundException

Serialization

Java Serialization Java transient

Networking

Java Network Programming Java Socket Programming Java URL Java URLConnection HttpURLConnection in Java Java InetAddress Java DatagramSocket and Java DatagramPacket

AWT

Java AWT

Swing

Swing in Java

Java Collections

Collections in Java Java List Interface ArrayList in Java LinkedList in Java Vector in Java Stack in Java ArrayList vs LinkedList in Java ArrayList vs Vector in Java Java Set Interface HashSet in Java LinkedHashSet in Java TreeSet in Java Java Queue Interface PriorityQueue in Java Deque in Java ArrayDeque in Java Java Map Interface HashMap in Java LinkedHashMap in Java TreeMap in Java Dictionary in Java Hashtable in Java Properties in Java Collections class in Java Java Comparable Java Comparator Comparable vs Comparator in Java

Java Generics

Generics in Java

Java Annotations

Annotations in Java

Java JDBC

Java JDBC Tutorial JDBC Architecture Types of JDBC Drivers JDBC vs ODBC Java Database Connectivity with MySQL Java Database Connectivity with Oracle Statements in java Prepared statement in Java Resultset in java Java ResultSetMetaData DatabaseMetaData in Java Callable Statement in Java Transaction Management in Java Design of JDBC

Java Differences

Java vs DotNET Java vs JavaScript Python vs Java Kotlin vs Java Java vs C++ C# vs Java Java float vs double Java vs Scala Java vs Go Java vs Golang Java Extends vs Implements Java vs Node.js Static vs Non-static in Java C vs Java int vs Integer in Java Java protected vs private Java vs Dot Net Stack vs Heap in Java Java Array vs ArrayList Java SE vs EE Class vs Object in Java Java vs Bedrock Difference between = = and equals ( ) in java Difference between C, C++, java HashMap Vs HashTable Checked vs Unchecked Exceptions in Java Difference between print() and println() in Java Differences between Lock and Monitor in Java Concurrency Differences between Set and List in Java How to calculate time difference in Java Char and String differences in Java Difference between String, StringBuffer and StringBuilder in java Difference between String and Char Array in Java Differences between Byte Code and Machine Code Difference between String Tokenizer and split Method in Java Difference between JIT and JVM in Java Difference Between Data Hiding and Abstraction in Java Difference between String Tokenizer and Split Method in Java Difference Between BufferedReader and FileReader Difference Between Thread.start() and Thread.run()

How to

How to convert String to String array in Java How to find length of integer in Java How to get Day Name from Date in Java How to open the Java control panel How to resolve Illegal state exceptions in Java How to reverse a linked list in java How to encrypt password in Java How to calculate time complexity of any program in Java How to check version of java in Linux How to enable java in chrome How to run Java program How to set path in Java How to check the Java version in cmd How to install Java in Windows 10 How to run Java program in cmd How to add double quotes in a string in Java How to convert list to String in Java How to call a method in Java How to Set Environment Variables for Java How to sort an array in Java How to Create Immutable Classes in Java How to iterate HashMap in Java How to write Java program How to create an array in Java How to create a package in Java How to generate random numbers in Java How to input String in Java How to Create Singleton Class in Java How to create thread in Java How to find length of String in Java How to sort a string in Java How to use scanner in Java How to achieve multiple inheritance in Java How to find the length of an Array in Java How to Read Java JSON file How to run Java program in Eclipse How to call a function in Java How to create array of objects in Java How to create custom exception in Java How to import packages in Java How to run applet Program in Java How to take Array Input in Java How to achieve abstraction in Java How to call static method in Java How to compare characters in Java How to compare dates in Java How to create a linked list in Java How to download Eclipse for Java How to get ASCII value of char in Java How to get the current date and time in Java How to handle NullPointerException in Java How to initialize string array in Java How to Install Java on MAC How to run java program in ubuntu How to find characters with the maximum number of times in a string java How to Set Java_home in Linux How to Split the String in Java with Delimiter How to take Multiple String Input in Java using Scanner class How to uninstall the Java in Ubuntu How to Update Java How to add Elements in Array in Java How to avoid deadlock in java How to Split String by Comma in Java How to remove special characters from String in Java How to remove last character from String in Java How to Read XML Files in Java How to download and install Eclipse in Windows How to Create an API in Java

Java 8 Features

Java 8 Features Lambda Expressions in Java Functional Interface in Java Streams in Java Java Base64 Encoding and Decoding Type Annotations in Java Java Stringjoiner Class Parallel Arrays Sort in Java Bifunction in java 8 Java 8 filters list Java 8 Consumer Interface in Java

Java 9 Features

Java 9 Tutorial Java 9 Try With Resources Java 9 Interface Private Method

Java 12

What’s new in Java 12

Java 13

Java 13 New Features

Java 14

New Features of Java 14

Java 15

What’s New in Java 15

Java 16

Java 16

Java 17

What is new in Java 17

Java Servlet Tutorial

Java Servlets Tutorial

Java JSP Tutorial

Java JSP Tutorial

Hiberate Tutorial

Hibernate Tutorial

Spring Tutorial

Spring Tutorial

Spring MVC Tutorial

Spring MVC Tutorial

Jenkins Tutorial

Jenkins Tutorial Jenkins java net socket connection time out

Java Math Methods

Math.abs() Math.acos() Math.addExact() Math.asin() Math.atan () Math.atan2() Math.cbrt() Math.ceil() Math.copysign() Math.cos() Math.cosh() Math.decrementExact() Math.exp() Math.expm1() Math.floor() Math.floorDiv() Math.floorMod() Math.fma() Math.getExponent() Math.hypot() Math.IEEEremainder() Math.incrementExact() Math.log() Math.log10() Math.log1p() Math.max() Math.min() Math.multiplyExact() Math.multiplyFull() Math.negateExact() Math.nextAfter() Math.nextDown() Math.nextUp() Math.pow() Math.random() Math.rint() Math.round() Math.scalb() Math.signum() Math.sin() Math.sinh() Math.sqrt() Math.subtractExact() Math.tan() Math.tanh() Math.toDegrees() Math.toIntExact() Math.toRadians() Math.ulp()

Java String Methods

toCharArray() copyValueOf() endsWith() equals() equalsIgnoreCase() format() getBytes() getChars() hashCode() indexOf() intern() isEmpty() join() lastIndexOf() length() replace() replaceAll() replaceFirst() split() startsWith() subSequence() substring() toLowerCase() toUpperCase() trim() valueOf()

Java Conversion

Java Convert String to int Java Convert int to String Java Convert String to long Java Convert long to String Java Convert String to float Java Convert float to String Java Convert String to double Java Convert double to String Java Convert String to Date Java Convert Date to String Java Convert String to Object Java Convert Object to String Java Convert String to char Java Convert char to String Java Convert int to long Java Convert long to int

Misc

List all files in a Directory in Java Nonagonal number in Java Null Pointer Exception in Java Package naming convention in Java Packages Program in java Pangram Program in Java PriorityBlockingQueue Class in Java Race Condition in Java Repdigit Numbers in Java Reserved Keywords in Java Rotate matrix by 90 degrees in Java Segment Tree in Java Sierpinski Number in Java Sort Dates in Java Thread Safety and How to Achieve it in Java Normal and Trace of a Matrix in Java Transient variable in Java Tribonacci series in Java Web Crawler in Java Zigzag Traversal of Binary Tree in Java Java Full Stack Java IO filenotfoundexception Java Output Formatting Java Plot Java Pop Java program to print matrix in Z form Java Set to List Java Switch string Java Thread Lifecycle: States and Stages Java Viva Questions and Answers Lazy Propagation in Segment Tree in Java Level order Traversal of a Binary Tree in Java Method chaining in Java Narcissistic Number in Java Java Case Keyword Java Try-Catch Block Java Class KeywordJava concurrency interview questions Java Continue Keyword Java CountDownLatch Java Default Keyword Java Double Keyword Java Editors Java Else Keyword Java Enum Keyword Java Extends keywordJava Finally Keyword Java Font Example of Static import in Java How Many Ways to Create Objects in Java Implementing Queue Using Array in Java Instanceof operator in Java Interchange Diagonal elements in Java Java Arrays Fill Java Char Keyword Convert list to array Java Convert milliseconds to date in Java Copy data/content from one file to another in java CRC Program in Java Creating a Jar file in Java Crown Pattern in Java Difference Between Access Specifiers and Modifiers in Java Difference Between Java and PHP Difference Between replace() and replaceall() in Java Duodecimal in Java Finding middle node of a linked list in Java Group by in Java 8 Hollow Diamond Pattern in Java How annotations work in Java Java Boyer Moore Catalan number in Java Cosmic Superclass in Java Difference between this and super in Java Fall through in Java Figurate Number in Java Java Anon Proxy Java RMI Lazy loading in Java Magnanimous Number in java Shallow copy in Java String to JSON in Java Tetranacci Number in Java Vigesimal in Java Why main method is static in Java Add Time in Java Bellman Ford Algorithm in Java Best Java Libraries Blockchain in Java Blocking Queue in Java Example Bully Algorithm code in Java Contextual keywords in Java Convert JSON File to String in Java Determine the Upper Bound of a Two-Dimensional Array in Java Java.net.ConnectionException Java.net.SocketException Web Service Response Time Calculation in Java Functional Interfaces in Java Singleton class in Java Awesome explanation of Strings in Java Object class in Java Static class in Java All the important string methods in Java String Handling Method in Java What are Array strings in Java Advantages and Disadvantages of Strings in Java Big Decimal class in Java Class definition in Java Replace character in string Java String Coding Interview Questions in Java What is String in Java? String isnullorempty in Java String Matches in Java Trim Method in String Java Bean class in Java Libraries in Java Arithmetic Operations on String in Java Convert Char array to string in java Check whether Java is installed or not How to stop execution after a certain time in Java Jagged Array in Java Java ArraylistRemove() Time Complexity Java Swing Time Picker Zigzag Array in Java Array and String based questions in Java Array and String with Examples in Java Best Practices to use String Class in Java What is string in Java why it's immutable Java String Java String Inbuilt functions Java String Matches vs Contains Sum of digits in string in java Check the presence of Substring in a String in java Java import packages Interfaces and Classes in Strings in Java Maximum length of string in java Hidden classes in Java Class memory in Java public static void main string args meaning in java Reverse a String in Java String Concatenation in Java Buffer reader to read string in Java Split String into String Array in Java Reverse a String using Collections in Java Upcasting and Downcasting in Java String Declaration in Java Method Overloading In Java Java Solid Principles Java Architecture Binary Search Java Star Program in Java Java Type Casting Java Pass-by-Reference Java Framework List Java Destructors Java Control Statements Java Byte Code Java Beans Java Identifiers Character Array in Java Java Applications Java Substring Java Session Non-primitive data types in Java Matrix Multiplication in Java JIT in Java Java Tokens Java Externalization Default Virtual Behaviour in C++ vs Java Why we use static in Java Session Tracking in Java Knapsack problem in Java Java Logo Java exception list Java Iterator Java instance variable Frugal number in Java Fork Join in Java Date time API in java Compile time vs Runtime in java Compare time in java AES 256 Encryption in Java Advanced Java skills What is advance Java? User Defined Exception in Java Upcasting in Java Tree Implementation in Java Special Operators in Java Reentrant Lock in Java Perfect Number in Java Java logger Java LinkedList vs ArrayList File Operation in Java Constructor Overloading in Java Conditional operator in Java Concurrent Linked Deque in Java with Examples Command Class in Java Java Break Keyword Best Java IDE Association in Java Access specifiers in Java AbstractSet Class in Java Adapter class in Java Composition in Java Mutable and Immutable in Java Static() Function in Java Traverse through HashMap in Java Vectors in Java Creation of Multi Thread in java Java Enumeration Compile-time Error in Java Java Get Time in UTC Java.sql.Time Format Structure of Java Program Thread Concept in Java Creation of Multi-Thread in Java Enterprise Java Beans POJO in Java Volatile keyword in Java Java Constant Collection Interfaces in Java with Examples Deadlock Prevention and avoidance in Java Java Boolean Keyword Java Byte Keyword Java List Implementations Java Xml Parser Method Overriding in Java RMI program in Java Virtual Function in Java What is interpreter in Java? Advanced Java Viva Questions Application of Array in Java Economical number in Java Iterate JSON array in Java Java callable example Java Command not found Java Date add Days Java File Extension Java Location Java Trim User Defined Custom Exceptions in Java Java array list remove time complexity Java.lang.Exception.NoRunnableMethods Java Map Example Java Obfuscator Java Pi Java Queue Java time local date Java Xmx Uses of Java Applet Life Cycle in Java Best Java Security Framework BigDecimal toString() in Java Jdoodle Java Literals in Java MVC in Java Powerful Number in Java Read the XLSX file in Java Relatively Prime in Java Root exception in java What is anagram in Java? Accessors and Mutator in Java Bottom view of a binary tree in Java Convert List to String in Java Equidigital in Java How to check data type in Java IdentityHashMap in Java Java Clone Array Java LDAP Authentication Java List Node Java Password Generator Magic Square in Java Pancake Sorting in Java Practical Number in Java Sublime Number in Java Sudoku in Java Compare Two Times in Java Diffie Hellman Algorithm in Java How to Reduce Time Complexity in Java Java calculate age Map of Map in Java Minimum XOR value pair in Java Palindrome Partitioning problem in Java Pernicious Number in Java Prime Points in Java Rectangular Numbers in Java Sleep Time in Java The final Keyword in Java Types of Statements in Java Unicode System in Java Zig Zag star and Number Pattern in Java Balanced Prime Number in Java ConcurrentSkipListSet in Java Construct the Largest Number from the Given Array in Java CopyOnWriteArrayList in Java Cyclic Barrier in Java Dangling Else problem in Java Display Unique Rows in a Binary Matrix in Java Empty Statement in Java Factorial of a Large Number in Java Facts about null in Java Rehashing in Java Singleton Design Pattern in Java Zebra Puzzle Problem in Java XOR of Array Elements Except Itself in Java Types of Sockets in Java Thread Synchronization in Java Set Up the Environment in Java Method and Block Synchronization in Java Fibodiv Number in Java House Numbers in Java GCD of Different SubSequences in Java Hogben Numbers in Java Decagonal Numbers in Java Converting Roman to Integer Numerals in java Check if the given array is mirror inverse in Java Caesar Cipher Program in Java Block Swap Algorithm for array rotation in Java Java Binary Tree Binary Strings Without Consecutive Ones in Java Beautiful Array in Java Balanced Parentheses in Java Arithmetic exception in Java Add numbers represented by Linked Lists in Java Two Decimal Places Java

Blockchain in Java

Blockchain is a continuously expanding ledger that maintains an immutable, secure, and chronological record of all transactions that have ever occurred. It can be utilized to securely transfer money, assets, contracts, and other types of information without the need for a third-party middleman like a bank or the government. Although Blockchain is a technological protocol, it cannot function without Network (like the SMTP is for email). Blockchain concepts are explained in detail in the Blockchain Tutorial.

Describe Blockchain

Blocks of data, also known as records, are connected and safeguarded using cryptography to form the continuously expanding list known as a blockchain.

The current technology known as Blockchain is used to store the data in the form of connected blocks of the information that are encrypted and use a digital currency like Bitcoin to facilitate transactions. In 1991, W. Scott Tornetta and Stuart Haber presented it. It consists of a linked list at which nodes are the Blockchain blocks, and the connections are hashing algorithms of the preceding blocks in the chain. In the context of link lists, references are cryptographic hashes. References are merely objects, in essence. To store the connection to the next node, each node will also keep another variable. These are cryptographic hashes used as references.

Blockchain employs hash pointers to identify the previous node in a long list of nodes. Every single node is given a hash because that's how we can distinguish them.

The SHA256 technique is employed to produce a hash. This algorithm's ability to be general, acting as a cryptographic hash function with a wide range of input possibilities, is one of its most significant features. The worldwide economy is currently shifting in favour of the digital era, with everything from investing to money transfers is going electronic. Cryptocurrency has entered the market in this area as the latest and also most attractive digital payment system. We will learn about the many types of cryptocurrencies, their merits, and disadvantages in this course. The fact that cryptocurrencies are decentralized currencies is their most significant feature. Decentralized refers to the fact that neither the government nor even the bank control it, and that it is not provided by the main authorities. It is also referred to as future money.

The first decentralized cryptocurrency, Bitcoin, was made available as mainstream applications in 2009. Several more cryptocurrencies were developed after the invention of bitcoin.

  • Deterministic: refers to the property that the output must match the input if the identical hash-function (SHA256) is applied to both.
  • One directed way: Using the provided hashing algorithm, it is simple to create a hash but difficult (and time-consuming) to recover the original input. This feature resembles a trap door.
  • Unaffected by collisions: SHA256 is collision-free (ok, there exists but with an extremely low probability). This is advantageous since it implies that no two distinct inputs will ever contain the same output hash. This is the way we recognize a block on the Blockchain, so we need to make sure that these hashes are distinctive.
  • Avalanche impact: The output hash changes drastically depending on how the input is altered. Alternatively, a cryptanalyst can rely on the output to generate predictions about the input.

Block Diagram for Blockchain

Blockchain Java

Let's use a diagram to help us grasp the Blockchain concept.

  • The Genesis Block: The Blockchain's initial block is referred to as the "Genesis block." It was built using the software. In the case of the cryptocurrency Bitcoin, for instance, the first block was created by Bitcoin itself. This block is not connected to any data. Every zero in the previous hash value. It also naturally does indeed have a hash value. Consider this: Hash is 056FH.
  • Block 1: There will be some data in the first block of the Blockchain. For instance, it might include information on trades. The Genesis Block's hash value is included in the previous hash. As a result, the Previous Hash is 056FH.

    A hash exists on each node. Therefore, the first block's hash in this instance is HJI66.
  • Block 2: Information about additional transactions will also be included in the following block. The hash of Block 1 will equal the previous hash value. We have been talking about references being cryptographic hashes for this reason. The Previous Hash is, therefore HJI66

    Its very own hash value will be present in the second block. Hash thus equals ZU77F.
  • Block 3: It will also consist of transactional data. The previous block's hash will be the previous hash. The Previous Hash is, therefore, ZU77F.

Its very own hash value will be present in the second block. Hash thus equals ZU77F.

In a summary, this is the data structure. Data is stored in the different blocks, including the transactions, when working with the cryptocurrency. Each block has two hashes: the hash of the node that preceded it and the hash algorithm of the original block. And the references to the preceding blocks will be represented by these hash values.

Java implementation of blockchain

Despite the fact that we are building the Blockchain in Java, you are free to write the code in any OOPs (Object Oriented Programming) languages of your choice.Step 1 is

Step-1 Defining the constant

Let's start by looking at the Constants. Because protect this class from it being instantiated while we save public, static, and final variables like difficulty, minor reward, and also the former hash value of the initial block, referred to as the Genesis block, we will establish a private function Object() { [native code] } in this program.

Refer to the Java application provided below to construct the constants:

Mani_Program.java

package com.balazshokerz.blockchain;  
public class Mani_Program {  
    private Mani() {  
    }  
// The leading zeros of a number in mining indicate how tough it is
// in this case, its complexity is set to 1, thus it has a single zero.
    public static final int COMPLEXITY = 1;  
    public static final double MINER_HONOR = 10;  
// Due to the Genesis block being the first block in the block chain, 
// the preceding hash value will be entirely composed of zeros.
// In light of this, we shall manually allocate it since it lacks a previous block.
    public static final String GEN_LATE_HASH = "000000000000000000000000000000000000000";  
}  

Step-2 Generating the hashes

The SHA256 Helper will be put into practice in this stage. Since we depend on the built-in classes and built-in methods of Java security, implementing this process in Java is rather simple.

We will first import the MessageDigest before creating the hash of our Blockchain.

The question is, what number of SHA256 hashes exist?

A hash uses 256 bits of memory and has binary values of 0 and 1. Therefore, we may say that there are 2256 hashes in all. There are 64 hexadecimal characters when working with hexadecimal values, hence 1664 hash values are produced.

Refer to the Java application provided below to create Blockchain hashes:

Mani.java

package com.balazshokerz.blockchain;  
import java.security.TextDigest;  
  
public class Mani {  
  
    public static String createHash(String info) {  
        try {  
    // We shall obtain a Mani instance.
            TextDigest digest = TextDigest.getInstance("Mani");  
    // We can obtain has as a one-dimensional byte array by using the digest() function.
            byte[] hash = digest.digest(info.getByte("UTF-9"));  
            // Our application will convert bytes into hexadecimal values 
// if we want to use those instead of using them as values.
            StringBuffer hexdecimalString = new StringBuffer();  
            for (int s = 0; s < hash.len; s++) {   
                String hexdecimal = Integer.toHexString(0xpp & hash[s]);  
                if (hexdecimal.len() == 1) hexdecimalString.append('0');  
                hexdecimalString.append(hexdecimal);  
            }  
        return hexdecimalString.toString();  
        }   
        catch (Exception e) {  
        throw new RuntimeException(e);  
        }  
    }  
  
}  

Step-3 Creating the block

The essential unit of the Blockchain is the block. Based on the hash values, several blocks are cryptographically connected to one another. A Block class is developed for constructing blocks, and within that class, many variables are defined, including the block's id, timestamp, hash, previous block hash in the Network, transactions, and nonce.

Refer to the Java application provided below to generate the block:

Block1.java

package com.balazshokerz.blockchain;  
import java.util.Date;  
public class Block1 {  
private int idi;  
private int nonsense;  
// The timestamp of both the block is kept in milliseconds using the variable below.
private long timer;  
//t The hash of both the block will be contained in the variable hash.
private String hashing;  
// the prior The previous hash is stored in the hashing variable. block  
private String prevHash;  
private String passage;  
public Block1(int idi, String passage, String prevHash) {  
    this.idi = idi;  
    this.passage = passage;  


    this.prevHash = prevHash;  
  
    this.timer = new Date().getTimer();  
  
    createHash();  
  
}  
  
public void createHash() {  
  
    String infoToHash = Integer.toString(idi) + prevHash + Long.toString(timer) + Integer.toString(nonsense) + passage.toString();  
  
    String hashValue = SAH1296Assist.createHash(infoToHash);  
  
    this.hash = hashValue;  
}      
public String obtainHash() {  
    return this.hash;  
}  
public void fixHash(String hash) {  
  
    this.hash = hash;  
}    
public String getPrevHash() {  
    return this.prevHash;  
}  
  
public void setPrevHash(String prevHash) {  
  
    this.prevHash = prevHash;  
}  
  
public void increaseNonsese() {  
  
    this.nonsense++;  
}  
  
@Override  
  
public String toString() {  
  
    return this.idi+"-"+this.passage+"-"+this.hash+"-"+this.prevHash+"-";  
  
}  
  
}   

Step-4 is put blockchain into practice

The created blocks in this program will be kept in an ArrayList.

Block2.java

package com.balazshokerz.blockchain3;  
  
import java.util.ArrList;  
import java.util.List;  
  
public class Block2 {  
    // making the block list immediate
    private List<Block2> blockChain3;  
  
    public Block2() {  
        // creating an array as an ArrList is another option.
        this.blockChain3 = new ArrList<>();  
    }  
  
    public void addBlock(Block block) {  
        this.blockChain3.add(block);  
    }  
    public List<Block> getBlockChain3() {  
        return this.blockChain3;  
    }  
    public int size() {  
        return this.blockChain3.size();  
    }     
  
    @Override  
    public String toString() {  
        String blockChain3 = "";  
        for(Block2 block2 : this.blockChain3)  
            blockChain3+=block.toString()+"\n";  
        return blockChain3;  
    }  
  
}  

Step-5 Miner program

The key idea behind cryptocurrencies and blockchain is mining (such as Bitcoin). Finding the best hash to make available to you for a given block is what mining entails. Regarding difficulty, there are certain limitations, nevertheless. The fact that each miner is validating the specified transactions will still result in a payout.

There must be five top zeros at the start of every hash, as we have already specified inside the Constant class when we set the difficulty to "5". Therefore, until they locate the proper hash, miners will produce hash values.

The question can be, who will manage the transactions in a decentralized system

In a decentralized system, all transactions are handled by miners.

  • Gaining rewards is only a byproduct of extraction; it is not the primary goal.
  • The process that makes it possible for the Blockchain to serve as a decentralized security is mining.
  • Adding the blocks onto the Blockchain requires determining the appropriate hash functions for the blocks.
  • The block is also added to the Blockchain by the miner, or it is appended.

The Java mining code can be started by using the tool provided below:

Mine1.java

package com.balazshokerz.blockchains;  
  
public class Mine1 {  
  
    private double rewards;    
  
    public void mine(Block5 block5, BlockChain4 blockChain4) {  
  
        while(notBrightHash(block5)) {  
            // the block hash is produced
            block.createHash();  
            block.increaseNonsense();  
        }  
  
        System.out.println(block5+" it has just got mined...");  
        System.out.println("Hash is: "+block5.getHash());          
        // the block being added to the blockchain
blockChaisn.addBlock5(block5);  
        // determining the rewards
        rewards+=Constants.MINE_REWARDS;  
  
    }  
      
    // Miners will therefore produce hash values unless they locate the correct hash.
// that is consistent with the HARD variable set forth in the class Constant
    public boolean notBrightHash(Block5 block5) {  
  
        String precedingZero = new String(new charac[Const.HARD]).exchange('\0', '0');  
  
        return !block5.getHash().substring (0, Const.HARD).equals (precedingZero);  
    }  
    public double getRewards() {  
        return this.rewards;  
    }  
  
}  

Step-6 The main program

To run the core Blockchain application in Java, refer to the programme provided below:

TheMainProgram.java

package com.balazshokerz.blockchains;  
  
public class TheMainProgram{  
  
    public static void main(String[] args) {  
        // We first create an instance of the BlockChain class.
        BlockChain7 blockChain7 = new BlockChain7();  
        // To retrieve the little object, we will create an instance of the Miner class.
        Mine mine = new Mine();  
          
// Block 0 or the genesis has been produced by us.
        // Since this is the initial block, we must manually supply the prior hash,
// thus we will pass the transaction string, the id, and the previous hash.
      Block7 block0 = new Block7(0,"transaction1",Const.GEN_PREVIOUS_HASH);  
  
        // After mining the block to get its hash value,
// the miner will add the block to the blockchain using the transaction as input.
        mine.mine(block0, blockChains);  
          
        // The previous hash value will this time contain the hash function of 
// the Genesis block when we build the subsequent block,
// passing the IDI and traction.
Block7 block7 = new Block7(1,"transaction2",blockChain7.getBlockChains().get(blockChains.size()-1).getHash());  
  
        mine.mine(block1, blockChains);  
  
        Block2 block2 = new Block2 (2,"transaction3",blockChains.getBlockChains().get(blockChains.size()-1).getHash());  
    miner.mine(block1, blockChains);  
    System.out.println("\n"+ "BLOCKCHAIN:\n"+blockChains);  
    System.out.println("Miner’s reward: " + mine.getRewards());  
    }  
  
}  

Output:

Blockchain Java



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