Implemented serialization

src/Main.java

@@ -8,9 +8,11 @@ public final class Main {
         System.out.print("Enter how many zeros the hash must start with: ");
         final var hashZeroes = sc.nextInt();
         final var blockChain = new BlockChain(hashZeroes);
+        blockChain.load();
 
-        IntStream.range(0, 5).forEach(blockChain::addBlock);
+        IntStream.range(0, 5).forEach(block -> blockChain.addBlock());
 
         System.out.println(blockChain);
+        blockChain.save();
     }
 }

src/model/Block.java

@@ -2,18 +2,20 @@ package model;
 
 import static java.lang.String.valueOf;
 
+import util.HashFunction;
+import java.io.Serializable;
 import java.util.Date;
 import java.util.Random;
-import util.HashFunction;
 
-public class Block {
+public class Block implements Serializable {
 
+  private static final long serialVersionUID = 1L;
   private final String previousBlockHash;
   private final int id;
   private final int hashZeroes;
   private final long timeStamp;
   private final String blockHash;
-  private final Random random = new Random();
+  private final transient Random random = new Random();
   private int magicNumber;
   private float generationSecs = 0;
 

src/model/BlockChain.java

@@ -1,5 +1,6 @@
 package model;
 
+import util.FileManagement;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -12,9 +13,10 @@ public class BlockChain {
     this.hashZeroes = hashZeroes;
   }
 
-  public void addBlock(final int id) {
+  public void addBlock() {
-    final String previousBlockHash = (id > 0) ? blockList.get(id - 1).getBlockHash() : "0";
+    final int nextId = blockList.size();
-    blockList.add(new Block(previousBlockHash, id, hashZeroes));
+    final String previousBlockHash = (nextId > 0) ? blockList.get(nextId - 1).getBlockHash() : "0";
+    blockList.add(new Block(previousBlockHash, nextId, hashZeroes));
   }
 
   public boolean validateBlockchain() {
@@ -41,4 +43,12 @@ public class BlockChain {
     }
     return blockList.stream().map(Block::toString).collect(Collectors.joining("\n"));
   }
+
+  public void load() {
+    FileManagement.loadBlockchain(blockList);
+  }
+
+  public void save() {
+    FileManagement.saveBlockchain(blockList);
+  }
 }

src/util/FileManagement.java

@@ -0,0 +1,42 @@
+package util;
+
+import model.Block;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.util.List;
+
+public final class FileManagement {
+
+  private static final String FILE = "blockChain.txt";
+
+  public static void saveBlockchain(final List<Block> blockList) {
+    final var file = new File(FILE);
+    try (final var fileOut = new FileOutputStream(file);
+        final var objectOut = new ObjectOutputStream(fileOut)) {
+      for (final var block : blockList) {
+        objectOut.writeObject(block);
+      }
+    } catch (final IOException e) {
+      e.printStackTrace();
+    }
+  }
+
+  public static void loadBlockchain(final List<Block> blockList) {
+    final var file = new File(FILE);
+    if (file.exists()) {
+      try (final var fileIn = new FileInputStream(file);
+          final var objectIn = new ObjectInputStream(fileIn)) {
+        while (fileIn.available() > 0) {
+          final var object = objectIn.readObject();
+          blockList.add((Block) object);
+        }
+      } catch (final IOException | ClassNotFoundException e) {
+        e.printStackTrace();
+      }
+    }
+  }
+}