Java implementation of blockchain concept

BlockChain.java

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Base64;
import java.util.Collection;
import java.util.List;

public class BlockChain {

	static class Block {
		private long index;
		private LocalDateTime timeStamp;
		private String data;
		private String previousBlockHash;
		private String currentHash;

		public Block(long index, LocalDateTime timeStamp, String data, String previousBlockHash) {
			super();
			this.index = index;
			this.timeStamp = timeStamp;
			this.data = data;
			this.previousBlockHash = previousBlockHash;
			String blockDetails = index + timeStamp.toString() + data + previousBlockHash;
			try {
				MessageDigest digest = MessageDigest.getInstance("SHA-256");
				byte[] hash = digest.digest(blockDetails.getBytes(StandardCharsets.UTF_8));
				currentHash = Base64.getEncoder().encodeToString(hash);
			} catch (NoSuchAlgorithmException e) {
				// if setup is correct this will not happen, do nothing
			}
		}

		public long getIndex() {
			return index;
		}

		public LocalDateTime getTimeStamp() {
			return timeStamp;
		}

		public String getData() {
			return data;
		}

		public String getPreviousBlockHash() {
			return previousBlockHash;
		}

		public String getCurrentHash() {
			return currentHash;
		}

		@Override
		public String toString() {
			return "Block [index=" + index + ", timeStamp=" + timeStamp + ", data=" + data + ", previousBlockHash="
					+ previousBlockHash + ", currentHash=" + currentHash + "]";
		}
	}

	Block genesis = new Block(0, LocalDateTime.now(), "Genesis Block", "0");
	List<Block> chain = new ArrayList<>();
	
	BlockChain() {
		chain.add(genesis);
	}
	
	Block getGenesisBlock() {
		return genesis;
	}

	int getSize() {
		return chain.size();
	}

	Collection<Block> getChain() {
		return chain;
	}

	Block createNextBlock(Block lastBlock) {
		long currentIndex = lastBlock.getIndex() + 1;
		Block block = new Block(currentIndex, LocalDateTime.now(), "new block #" + currentIndex, lastBlock.getCurrentHash());
		chain.add(block);
		return block;
	}

	public static void main(String[] args) {
		BlockChain blockChain = new BlockChain();
		int numberOfBlocks = 20;
		Block last = blockChain.getGenesisBlock();
		for (int i = 0; i < numberOfBlocks; i++) {
			Block next = blockChain.createNextBlock(last);
			System.out.println("Block " + next.getIndex() + " added: " + next.getCurrentHash());
			last = next;
		}
		System.out.println();
		System.out.println("Block chain length: " + blockChain.getSize());
		for (Block block : blockChain.getChain()) {
			System.out.println(block);
		}
	}

}