Initial commit

src/model/BlockChain.java

@@ -0,0 +1,44 @@
+package model;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class BlockChain {
+  private final int hashZeroes;
+  private static final List<Block> blockList = new LinkedList<>();
+
+  public BlockChain(final int hashZeroes) {
+    this.hashZeroes = hashZeroes;
+  }
+
+  public void addBlock(final int id) {
+    final String previousBlockHash = (id > 0) ? blockList.get(id - 1).getBlockHash() : "0";
+    blockList.add(new Block(previousBlockHash, id, hashZeroes));
+  }
+
+  public boolean validateBlockchain() {
+    if (blockList.isEmpty()) {
+      return true;
+    }
+
+    final List<String> previousHashes = blockList.stream().map(Block::getPreviousBlockHash).collect(
+        Collectors.toList());
+    final List<String> hashes = blockList.stream().map(Block::getBlockHash).collect(Collectors.toList());
+
+    for (var index = 1; index < hashes.size(); index++) {
+      if (!previousHashes.get(index).equals(hashes.get(index - 1))) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  public String toString() {
+    if (!validateBlockchain()) {
+      System.out.println("Blockchain invalid!");
+    }
+    return blockList.stream().map(Block::toString).collect(Collectors.joining("\n"));
+  }
+}