用Java数据结构代码实现一个简单的10个区块的区块链

好的，以下是使用Java实现一个简单的10个区块的区块链的代码：

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Date;

public class Block {
    private int index;
    private Date timestamp;
    private String data;
    private String previousHash;
    private String hash;

    public Block(int index, Date timestamp, String data, String previousHash) {
        this.index = index;
        this.timestamp = timestamp;
        this.data = data;
        this.previousHash = previousHash;
        this.hash = calculateHash();
    }

    public String calculateHash() {
        String dataToHash = Integer.toString(index) + previousHash + Long.toString(timestamp.getTime()) + data;
        MessageDigest digest;
        String encoded = null;

        try {
            digest = MessageDigest.getInstance("SHA-256");
            byte[] hash = digest.digest(dataToHash.getBytes("UTF-8"));
            StringBuilder hexString = new StringBuilder();

            for (byte b : hash) {
                String hex = Integer.toHexString(0xff & b);
                if (hex.length() == 1) {
                    hexString.append('0');
                }
                hexString.append(hex);
            }

            encoded = hexString.toString();
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        return encoded;
    }

    public int getIndex() {
        return index;
    }

    public Date getTimestamp() {
        return timestamp;
    }

    public String getData() {
        return data;
    }

    public String getPreviousHash() {
        return previousHash;
    }

    public String getHash() {
        return hash;
    }
}

public class BlockChain {
    private ArrayList<Block> blocks;

    public BlockChain() {
        this.blocks = new ArrayList<Block>();
        this.blocks.add(createGenesisBlock());
    }

    private Block createGenesisBlock() {
        return new Block(0, new Date(), "Genesis Block", "0");
    }

    public void addBlock(Block block) {
        block.previousHash = blocks.get(blocks.size() - 1).getHash();
        block.hash = block.calculateHash();
        blocks.add(block);
    }

    public Block getLatestBlock() {
        return blocks.get(blocks.size() - 1);
    }

    public boolean isChainValid() {
        for (int i = 1; i < blocks.size(); i++) {
            Block currentBlock = blocks.get(i);
            Block previousBlock = blocks.get(i - 1);

            if (!currentBlock.getHash().equals(currentBlock.calculateHash())) {
                return false;
            }

            if (!previousBlock.getHash().equals(currentBlock.getPreviousHash())) {
                return false;
            }
        }

        return true;
    }
}

public class Main {
    public static void main(String[] args) {
        BlockChain blockchain = new BlockChain();
        blockchain.addBlock(new Block(1, new Date(), "Transaction Data 1", ""));
        blockchain.addBlock(new Block(2, new Date(), "Transaction Data 2", ""));
        blockchain.addBlock(new Block(3, new Date(), "Transaction Data 3", ""));
        blockchain.addBlock(new Block(4, new Date(), "Transaction Data 4", ""));
        blockchain.addBlock(new Block(5, new Date(), "Transaction Data 5", ""));
        blockchain.addBlock(new Block(6, new Date(), "Transaction Data 6", ""));
        blockchain.addBlock(new Block(7, new Date(), "Transaction Data 7", ""));
        blockchain.addBlock(new Block(8, new Date(), "Transaction Data 8", ""));
        blockchain.addBlock(new Block(9, new Date(), "Transaction Data 9", ""));
        blockchain.addBlock(new Block(10, new Date(), "Transaction Data 10", ""));

        System.out.println("Is the blockchain valid? " + blockchain.isChainValid());
    }
}

在这个代码中，我们首先定义了一个Block类来表示一个区块。该类包括区块的索引、时间戳、数据、前一个区块的哈希值和自身的哈希值，以及计算哈希值的方法。

然后，我们定义了一个BlockChain类来表示整个区块链。该类包括一个ArrayList来存储所有的区块，以及添加区块、获取最新区块和验证区块链等方法。

在主函数中，我们创建一个新的区块链，并添加了10个区块。最后，我们打印出区块链的有效性。

需要注意的是，这只是一个最简单的区块链实现。在实际应用中，还需要考虑更多的问题，例如如何防止双重支付、如何保证区块链的安全性等。