区块链(一)

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//区块代码演示
public class Block {
    
    public long index;//序列
    public long timeStamp;//生成的时间戳
    public String hashSelf;//本区块体的hash
    public String hashPre;//上一个区块的hash
    public long nonce;//随机数，用于生成的hash符合复杂度
    public String data;//数据

    public Block(long index, String hashPre, String data) {
        this.index = index;
        this.hashPre = hashPre;
        this.data = data;
        this.timeStamp = new Date().getTime();
        this.hashSelf = StringUtil.sha256(index + timeStamp + hashPre + data);
    }
}

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//hash函数
public class StringUtil {

    /**
     * sha256加密城256位的hash值
     */
    public static String sha256(String input) {
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] hash = digest.digest(input.getBytes("UTF-8"));
            StringBuilder hexString = new StringBuilder();
            for (byte aHash : hash) {
                String hex = Integer.toHexString(0xff & aHash);
                if (hex.length() == 1) hexString.append('0');
                hexString.append(hex);
            }
            return hexString.toString();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}