用java编写一个区块链程序,用java编写一个区块链数据库

区块链是一种分布式数据库技术，它能够存储和管理大量的数据。它是一种有效的、可靠的、安全的、可信赖的数据库技术，它能够有效地追踪、记录和管理各种数据。本文将介绍区块链数据库拓展的三个关键词：去中心化，加密和可验证性。

去中心化：去中心化是区块链技术的一个重要特点，它意味着没有中央服务器，没有中央控制者。区块链数据库是一个分布式数据库，它有多个节点，每个节点都是独立的，没有中央节点来控制和管理它们。这样，即使某个节点出现故障，也不会影响整个系统的运行，从而提高了系统的可靠性。

加密：加密是区块链技术的另一个重要特点。它使用密码学技术来加密数据，以防止数据被窃取或篡改。区块链数据库使用哈希函数对数据进行加密，这样，即使数据被窃取，也无法被破解。它还使用非对称加密技术，以便节点之间的通信是安全的，从而保护数据的隐私。

可验证性：可验证性是区块链技术的另一个重要特点。它使用共识算法，以便节点之间可以达成一致，以此来验证数据的有效性。区块链数据库使用共识算法，以便节点之间可以达成一致，以验证数据的有效性。这样，即使某个节点出现故障，也不会影响数据的完整性和可靠性。

区块链数据库拓展的这三个关键词：去中心化，加密和可验证性，都是区块链技术的重要特点，它们使得区块链技术具有可靠性、安全性和可信赖性，从而为数据的安全管理提供了可靠的保障。

A. Beijing Java course shares the consensus algorithm in blockchain technology

We have shared some explanations and knowledge point analysis about blockchain technology with you many times . Today, in the Beijing Java course, we will learn about some basic definitions and characteristics of consensus algorithms in blockchain technology.

A brief look at the blockchain

The chain in our general ideology is an iron chain, made of iron. One link after another. Figuratively, the blockchain can also be understood in this way, except that it is not made of iron, but connected by blocks with a certain data structure. This is a simple prototype

Popular explanation of consensus

The so-called consensus, in layman’s terms, means that we all agree on the understanding of something. For example, we have daily meetings to discuss issues, or we can judge whether an animal is a cat. After looking at it with the naked eye, we feel it looks like a cat. If it meets the characteristics of a cat, then we think it is a cat. Consensus is a rule.

Continue to use our meeting example. Participants in the meeting discuss and solve problems through meetings.

Compared with the blockchain, miners participating in mining use a certain consensus method (algorithm) to make their own ledger consistent with the ledgers of other nodes. The deeper meaning of keeping the ledger consistent is to keep the block information in the chain consistent.

Why is consensus needed? Is it possible to not need it? Of course not. Without the rules of consensus in life, everything will be chaotic. The blockchain loses consensus rules, and each node does its own thing, losing its consistent meaning.

The corresponding relationship between these two examples is as follows:

Meeting people = mining miners

Meeting = consensus method (algorithm)

Talk about solving problems = make your own ledger consistent with the ledgers of other nodes

If you don’t understand the concept of a node, please first understand it as a miner. A node contains many roles, and miners are one of them.

Consensus algorithm

Currently in the blockchain, nodes allow their own ledgers to match those of other nodes. There are several consensus methods (algorithms) that maintain consistency:

PoW, represented by Bitcoin (BTC)

Disadvantages:

The emergence of mining pools violates the original intention of decentralization to a certain extent, and also makes 51% attacks possible, affecting its security.

There is a huge waste of computing power. Look at the mining pool that consumes a lot of electricity resources. As the difficulty increases, not enough is mined to pay the electricity bill

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PoS, represented by Ethereum (ETH), transitioning from PoW to PoS

Disadvantages:

The cost of saboteurs attacking the network is very low, and they can compete if they own tokens

In addition, nodes with a large number of tokens gain accounting rights The probability will be greater, which will make the network consensus dominated by a few wealthy accounts, thus losing fairness.

B. Java course shares the component architecture of blockchain technology

With the continuous development of the Internet, more and more people have learned about it Regarding some characteristics and usage of blockchain technology, today we will introduce some elements of blockchain.

The composition of blockchain

Blockchain consists of blocks and chains. Each block contains three elements: data, hash value, and the hash value of the previous block.

The first element of the block is data. The data stored in the block is related to the type of blockchain. For example, blocks in the Bitcoin blockchain store relevant transaction information, including the seller, buyer, and the amount of Bitcoin traded.

The second positive element of the block is the hash value. Each block contains a hash value, which is used to identify a block and all the content it contains. Once a block is created, its hash value is calculated accordingly. Changing something in the block will cause the hash value to change. So in other words: hashes are helpful when you want to detect changes to the contents of a block. If a block's fingerprint changes, it is no longer the same block as before.

The third element of the block is the hash value of the previous block. This element allows links to be formed between blocks and makes the blockchain very secure.

As an example, suppose we have a blockchain containing 3 blocks. Each block contains its own hash and the hash of the previous block. Block No. 3 points to block No. 2, and block No. 2 points to block No. 1. But block No. 1 is a bit special. It cannot point to the previous block because it is the first block. We call block 1 the genesis block.

So, now let's say you tampered with the second block. This will cause the hash value of the second block to change, so the data stored in block 3 will be wrong and illegal. Once the data stored in block No. 3 is illegal, the subsequent blocks must also be illegal.

So if a person wants to tamper with any block in the blockchain, he must modify this block and all blocks after this block. This will be an onerous task.

Blockchain proof of work

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However, simply using hash values ​​is not enough to prevent users from tampering with blocks. Because today's computers are powerful enough to calculate thousands of hash values ​​per second. The Java course suggests that you can completely tamper with a block and recalculate the hash values ​​of other blocks, thus making your block legal again.

C. Introduction to blockchain technology, which programming languages ​​are involved

Go language

Go language (Golang) is Google’s 2009 A new programming language introduced in 2019 that can reduce the complexity of code without sacrificing application performance. Rob Pike, chief software engineer at Google, said: "We developed Go because the difficulty of software development over the past 10 years or so has been frustrating."

In addition to Bitcoin being developed in C, At present, the clients of most mainstream workshops are developed with Go language, which is enough to show the status of Go language in the entire blockchain industry.

C

C further expands and improves the C language and is an object-oriented programming language. C runs on a variety of platforms, such as Windows, MAC operating systems, and various versions of UNIX. C is a very widely used computer programming language. It is a general programming language that supports multiple programming patterns, such as procedural programming, data abstraction, object-oriented programming, generic programming, and design patterns.

Most blockchain companies choose to use C to write the bottom layer of the blockchain. The most famous ones are Bitcoin, Ripple, etc., which mainly reflect strong computation.

Java

Java is different from general compiled languages ​​or interpreted languages. It first compiles the source code into bytecode, and then relies on virtual machines on various platforms to interpret and execute the bytecode, thereby achieving the cross-platform feature of "write once, run anywhere". The development of blockchain projects has obvious dependence on Java.

Others include Python, system architecture, Ethereum, Linux, hyperledger, JavaScript, etc. will be covered.

D. Why no one uses java to write blockchain

Some people are using java to do it.

Blockchain projects have relatively high efficiency requirements, so most core source code development uses c/c++. But if you are doing a blockchain project, unless you need to make a lot of adjustments to the source code, you will not choose to use Java.

For general dapp applications, it should also be a good choice to use java to develop. For example, for the Ethereum blockchain, there is the web3j class library for Java, which is very convenient; for Bitcoin, there is the bitcoinj class library, which is also very easy to use. returnIt depends on what level of application it is, what it is going to do, and the situation of the team.

Java is an object-oriented programming language. It not only absorbs the various advantages of the C++ language, but also abandons the difficult-to-understand concepts such as multiple inheritance and pointers in C++. Therefore, Java The language has two characteristics: powerful and easy to use.

As a representative of static object-oriented programming languages, the Java language perfectly implements object-oriented theory and allows programmers to perform complex programming with an elegant way of thinking.

Java has the characteristics of simplicity, object-oriented, distributed, robustness, security, platform independence and portability, multi-threading, and dynamics. Java can write desktop applications, Web applications, distributed systems and embedded system applications, etc.