reading data stored into blockchain

Question

I've implemented a simple blockchain in java using arraylist contain object (block class).

    public static ArrayList<Block> blockchain = new ArrayList<Block>();

... and block class containing the transaction which I need to store into blockchain.

  public Block(transaction data,String previousHash ) {

    this.data = data;

    this.previousHash = previousHash;

    this.timeStamp = new Date().getTime();


              this.hash = calculateHash(); 
}

transaction class contains the data: hash of medical record title of file medical record .....

    public transaction(String title,String date,String pointer,int version,int nbdoctor,int nbsdoctor ,byte[] patient 
        ,String hashdata , ArrayList<byte []> permission , ArrayList<byte []> spermission ,byte[] newdoctorkey , byte[] newsdoctorkey ,
        byte[] removedoctor ,byte[] sremovedoctor) 

but I don't know the way to read from this blockchain . I want to get the data into transaction object according to the title field. I want a quick method to access to the data into blockchain (into array list).

Thank you.

Answer 1

The answer to this question is simple and straightforward. To read data which is stored in blocks within blockchains, you need a 'block explorer.'

Now depending on the type of blockchain you are vested in, you should chose relevant block explorers. For a bitcoin blockhain, you need a bitcoin explorer; and similarly for an ethereum blockchain, you need an Ethereum explorer.

Answer 2

You seem to have trouble understanding the block concept. A block always contains multiple transactions in a blockchain. These transactions are structured as a Merkle tree to improve read/write performance. If you only place a single transaction inside a block, there is no point in using a block. At that point you might as well use a simple hash chain, where each transaction contains a reference to its predecessor.

For more, refer to: https://en.wikipedia.org/wiki/Blockchain