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Blockchain implementation for toutsurlebitcoin.fr
package fr.toutsurlebitcoin.myblockchain;
import java.util.ArrayList;
import java.util.List;
public class Blockchain {
private int difficulty;
private List<Block> blocks;
public Blockchain(int difficulty) {
this.difficulty = difficulty;
blocks = new ArrayList<>();
// create the first block
Block b = new Block(0, System.currentTimeMillis(), null, "First Block");
b.mineBlock(difficulty);
blocks.add(b);
}
public int getDifficulty() {
return difficulty;
}
public Block latestBlock() {
return blocks.get(blocks.size() - 1);
}
public Block newBlock(String data) {
Block latestBlock = latestBlock();
return new Block(latestBlock.getIndex() + 1, System.currentTimeMillis(),
latestBlock.getHash(), data);
}
public void addBlock(Block b) {
if (b != null) {
b.mineBlock(difficulty);
blocks.add(b);
}
}
public boolean isFirstBlockValid() {
Block firstBlock = blocks.get(0);
if (firstBlock.getIndex() != 0) {
return false;
}
if (firstBlock.getPreviousHash() != null) {
return false;
}
if (firstBlock.getHash() == null ||
!Block.calculateHash(firstBlock).equals(firstBlock.getHash())) {
return false;
}
return true;
}
public boolean isValidNewBlock(Block newBlock, Block previousBlock) {
if (newBlock != null && previousBlock != null) {
if (previousBlock.getIndex() + 1 != newBlock.getIndex()) {
return false;
}
if (newBlock.getPreviousHash() == null ||
!newBlock.getPreviousHash().equals(previousBlock.getHash())) {
return false;
}
if (newBlock.getHash() == null ||
!Block.calculateHash(newBlock).equals(newBlock.getHash())) {
return false;
}
return true;
}
return false;
}
public boolean isBlockChainValid() {
if (!isFirstBlockValid()) {
return false;
}
for (int i = 1; i < blocks.size(); i++) {
Block currentBlock = blocks.get(i);
Block previousBlock = blocks.get(i - 1);
if (!isValidNewBlock(currentBlock, previousBlock)) {
return false;
}
}
return true;
}
public String toString() {
StringBuilder builder = new StringBuilder();
for (Block block : blocks) {
builder.append(block).append("\n");
}
return builder.toString();
}
}
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