This course will give you a full introduction into all of the core concepts in blockchain, smart contracts, solidity, NFTs/ERC721s, ERC20s, Coding Decentralized Finance (DeFi), python and solidity, Chainlink, Ethereum, upgradable smart contracts, and full stack blockchain development. Follow along with the videos and you’ll be a blockchain wizard in no time! 💻 The repository with helpful links to all code, resources, and support forums is located here: https://github.com/smartcontractkit/f… Please reference the repo for anything you need, and feel free to leave issues, jump into the discussions, and more. ⭐️ Course Contents ⭐ ⌨️ (00:00:00) Introduction ⌨️ (00:06:33) Lesson 0: Welcome To Blockchain ⌨️ (01:31:00) Lesson 1: Welcome to Remix! Simple Storage ⌨️ (02:09:32) Lesson 2: Storage Factory ⌨️ (02:26:35) Lesson 3: Fund Me ⌨️ (03:26:48) Lesson 4: Web3.py Simple Storage ⌨️ (04:27:55) Lesson 5: Brownie Simple Storage ⌨️ (05:06:34) Lesson 6: Brownie Fund Me ⌨️ (06:11:38) Lesson 7: SmartContract Lottery ⌨️ (08:21:02) Lesson 8: Chainlink Mix ⌨️ (08:23:25) Lesson 9: ERC20s, EIPs, and Token Standards ⌨️ (08:34:53) Lesson 10: Defi & Aave ⌨️ (09:50:20) Lesson 11: NFTs ⌨️ (11:49:15) Lesson 12: Upgrades ⌨️ (12:48:06) Lesson 13: Full Stack Defi ⌨️ (16:14:16) Closing and Summary ✏️ Course developer by Patrick Collins, check out his YouTube channel for more great programming courses, blockchain education, and fun: https://www.youtube.com/c/patrickcollins Follow Patrick! 🐦Twitter: https://twitter.com/PatrickAlphaC 📺YouTube: https://www.youtube.com/channel/UCn-3… ✍️Medium: https://medium.com/@patrick.collins_5… 💻GitHub: https://github.com/PatrickAlphaC 🏢LinkedIn: https://www.linkedin.com/in/patrickal…>
⌨️ (00:00:00) Introduction ⌨️ (00:06:33) Lesson 0: Welcome To Blockchain
Dapp =Smart Contract =Decentralized App
Understanding Ethereum means we will understand the majority of these platforms.
Bitcon was the first one to take blockchain mainstream.
Bitcon is like a digital gold.
Ethereum allows for smart contracts.
chainlink provides data and external computation to smart contracts.
Features and massive advantages of blockchain and smart contracts：
1.decentralized
2.Transparency& flexibility. We can see every changes in the chain. Everyone follow the same rules.
3.Speed and efficiency
4.security and immutability
5.Removal of counterparty risk
6.Trust minimized agreements
7.Hybrid Smart Contracts combine on and off-chain
Download metamask:
Ethernscan:https://etherscan.io/ : A application that allows us see the details of blockchain.
Testnets are free and for testing smart contracts , mainnet cost money and are considered “live “
Mining:The process of finding the “solution” to the blockchain “problem”.
In our example, the “problem” was to find a hash that starts with four zeros.
Nodes get paid for mining blocks.
Block: A list of transactions mined together
Decentralized: Having no single point of authority
Private Key->>>Public Key->>>>>address
Blockchain nodes keep lists o f the transactions that occur
Consenus: the mechanism used to agree on the state of a blockchain
1.Chain Selection
—Nakamoto Consensus(a combination of proof of work and longest chain rule the decentralized)
)
2.Sybil Resistance
–proof of work(ETH/Bitcon) miner
–proof of stake validators
Proof of Work uses a lot of energy
Transaction fee- first one to find the transaction
Block reward - first node to solve the problem
Gas fees are paid by whoever makes the transaction.
Two types of Attack:
1.sybil attack:when a user creates a whole bunch of pseudo-anonymous accounts to try to influence the network
2.51% attack: some one have longest chain and more than 51 percent of the rest of the network can fork
Longest chain rules: Other nodes always follow the longest chain
Proof of Stake
avalanche solana polygon polkadot and terra and Ethereum2.0 using it
How it works? —-Proof of stake nodes put up collateral as a sybil resistance mechanism
Randomness –choose the random node
Proof of stake use much less energy
Sharding：Eth2.0 implemente this new methodology called sharding to sovle the scalability problem(分片) . which can incredibly increase the number of block space and greatly increase the number of transactions on a blockchain
Layer 1: Base layer blockchain implementation
Layer 2: Any application built on top of a layer 2
Rollups: a rollup is kind of like a sharded chain they derive from the layer one like ethereum and they bulk send their transactions onto the layer one.(Unlike side chains:because side chains derive their security from their own protocols)
Conclusions:
ETH and BTC are Proof Of Work(at the time of recording)
ETH 2.0 will be Proof of Stake
PoW & PoS are sybil resistance mechanisms
The bigger the blockchain,the more secure
Consensus is how blockchains decide what the state of the chain
Sharding and rollups are scalabilityb solutions
Only so many transactions can fit into a block
Gas prices are how much it costs to perform executions on-chain
class Person { int age; void shout() {System.out.println(“oh,my god! I am “ + age);} } age是类的属性 ，也叫类成员变量 。 shout是方法也叫类的成员函数。 shout方法可以直接访问同一个类中的age变量 ，如果一个方法中有与成员变量同名的局部变量，该方法中对这个变量名的访问是局部变量，而不再是成员变量。
public class SimpleClassToShowThis{ public int a; public void test(){ int a=50; this.a=a+5; System.out.println(a); } }
Public class TestThis{ public static void main(String[] args){ SimpleClass simple=new SimpleClass(); simple.test(); System.out.print(“simple对象中a的值为:”)； System.out.println(simple.a); }
eg: int[] a; double d[]; String[] args; Person p[];
Java语言中声明数组类型的变量时不允许指定数组的长度(数组中元素的个数)
如：int a[3] //非法
创建并使用数组：
4.2 多维数组
多维数组可以理解为由若干个低维数组所组成的数组。
•Java中多维数组的声明和初始化应按从高维到低维的顺序进行。
•Java中多维数组不必须是规则矩阵形式。
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eg: int a[][]= {{1,2},{3,4,0,9},{5,6,7}}; int[][] a = new int[3][4]; int[][] t = new int[3][]; t[0] = new int[4]; t[1] = new int[2]; int[][] b = new int[][4];
4.2.1多维数组初始化
静态初始化
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int a[][] = {{1,2},{2,3},{3,4,5}}; int b[3][2] = {{1,2},{2,3},{4,5}}; //非法
动态初始化
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int a = new int[3][]; a[0] = new int[2]; a[1] = new int[4]; a[2] = new int[3]; a[0][0] = 45; a[0][1] = 87; …… a[2][2] = 99;
import java.util.*; public class ArrayDemo { public static void main(String args[]) {String[] s1={"zhangsan","lisi","wangwu","liliu","yaoqi"}; String[] s2={"zhangsan","lisi","wangwu","liliu","yaoqi"}; System.out.println(Arrays.equals(s1,s2)); Arrays.sort(s1); for(int i=0;i<s1.length;i++) {System.out.println(s1[i]); } } } True Liliu Lisi Wangwu Yaoqi zhangsan
4.3 字符数组
4.3.1字符串的声明与创建
声明字符串的格式是：String stringName；
字符串的创建格式： stringName = new String（字符串常量）;
或者 stringName =字符串常量;
举例：str= new String ( “student” );
str= “student” // 内存位置在专用的字符串区内
用一个已创建的字符串创建另外一个字符串：
s=“abc123”;
String t=String(s);
用字符数组创建：
char a[]={“W”,”H”,”U”,”T”};
String b=new String(a);
4.3.2与字符串有关的方法
确定字符串的长度 ：
public int length()
取得字符：
public char charAt(int index)
取得子串：
public String substring(int beginIndex)
public String substring(int beginIndex,int endIndex)
字符串内容的比较
public int compareTo(String stringName2)
public int compareToIgnoreCase(String stringName2)
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public static void main(String args[]){ String s = new String("武汉理工大学计算机学院"); System.out.println(s + " 的长度：" + s.length()); System.out.println(s + " 第三个字：" + s.charAt(2) ); System.out.println(s + " 的子串： " + s.substring(6)); String s1 = new String("ABCDE"); String s2 = new String("ABCED"); System.out.println("\"ABCDE\"和\"ABCED\"比较结果："+s1.compareTo(s2)); } 武汉理工大学计算机学院 的长度：11 武汉理工大学计算机学院 第三个字：理 武汉理工大学计算机学院 的子串： 计算机学院 "ABCDE"和"ABCED"比较结果：-1
字符串连接:
public String concat(String stringName2)
字符串检索:
public int indexOf(int ch) public int indexOf(int ch,int fromIndex) public int indexOf(String stringName2) public int indexOf(String stringName2,int fromIndex)
字符数组转换为字符串:
public static String copyValueOf(char []ch1) public static String copyValueOf(char []ch1,int cBegin,int cCount)
public static String valueOf(boolean b) public static String valueOf(char c) public static String valueOf(int i) public static String valueOf(long L) public static String valueOf(float f) public static String valueOf(double d)
字符串大小写转换
public String toUpperCase() public String toLowerCase()
字符串内容的替换：
public String replace(char oldChar,char newChar)
删除字符串的前导空白和尾部空白：
public String trim()
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public static void main(String args[]){ String s = new String("武汉理工大学计算机学院"); String s1 = ""; String s2 = "ABCDEFG"; char a[] = s.toCharArray() ; int i =1000; System.out.println("字符串转换为字符数组并输出第一位: "+a[0]); System.out.println(s1.valueOf(i)); System.out.println(s2.toLowerCase()); } 字符串转换为字符数组并输出第一位: 武 1000 abcdefg
4.3.3字符串缓冲区
StringBuffer的构造
public StringBuffer()
构造一个其中不带字符的字符串缓冲区，其初始容量为 16 个字符。
public StringBuffer(int capacity)
构造一个不带字符，但具有指定初始容量的字符串缓冲区。
public StringBuffer(String str) 构造一个字符串缓冲区，并将其内容初始化为指定的字符串内容。该字符串的初始容量为 16 加上字符串参数的长度。
编译程序：
