Stage #3: Miners and mining complexity

src/blockchain/Blockchain.java

@@ -0,0 +1,166 @@
+import java.security.MessageDigest;
+import java.time.LocalTime;
+import java.util.ArrayList;
+
+public class Blockchain extends  Thread {
+
+    volatile static ArrayList<String> block = new ArrayList<>();
+
+    private String nonce;
+    volatile static int starthash = 0;
+    volatile static int zeros = 0;
+    private int no;
+    volatile static int id = 1;
+    volatile static boolean blockCLOSE;
+    volatile  static int winner = 0;
+
+    String previoushash = Integer.toString(starthash);
+    String currenthash = "";
+    private int tiktok;
+    private long timestamp;
+
+    volatile static int check = 0;
+
+
+    Blockchain(int no) {
+        this.no = no;
+    }
+
+    @Override
+public void run(){
+
+        if(!block.contains("0")){
+            block.add("0");
+        }
+
+        for (int i = 0;  ; i++){
+            nonce = "";
+            for(int k = 0; k  < zeros; k ++){
+                this.nonce+="0";
+
+            }
+            currenthash = proofOfWork(block.get(i));
+            if (currenthash.equals("null")) {
+                while (block.size()==id){
+                    try {
+                        Thread.sleep(2_000);
+                    } catch (InterruptedException e) {
+                        e.printStackTrace();
+                    }
+                }
+            } else {
+
+                getTimeStamp();
+
+
+                System.out.println("Block:");
+                System.out.println("Created by miner # " + no);
+                System.out.println("id: " + id);
+                System.out.println("Timestamp: " + timestamp);
+                System.out.println("Hash of the previous block: " + block.get(i));
+                System.out.println("Hash of the block: " + currenthash);
+                System.out.println("Block was generating for " + tiktok + " seconds");
+                id++;
+                block.add(i+1, currenthash);
+
+                if (tiktok > 59) {
+                    zeros--;
+                    System.out.println("N was decreased by 1");
+                } else if(tiktok>10) {
+                    //the same
+                    System.out.println("N stays the same");
+                }else {
+                    zeros++;
+                    System.out.println("N was increased to "+zeros);
+                }
+                System.out.println();
+
+            }
+
+        }
+
+
+    }
+
+    private void getTimeStamp() {
+        this.timestamp = System.currentTimeMillis();
+    }
+
+
+    private String proofOfWork(String block) {
+
+        String nonceKey = nonce;
+        long nonce = 0;
+        boolean nonceFound = false;
+        blockCLOSE = false;
+        String nonceHash = "";
+
+
+        LocalTime time_before = LocalTime.now();
+
+        while (!nonceFound) {
+
+    nonceHash = GenerateBlock(block + nonce);
+
+    nonceFound = nonceHash.substring(0, nonceKey.length()).equals(nonceKey);
+    synchronized (Thread.currentThread()) {
+    if(check == 0) {
+
+        if (nonceFound == true) {
+            this.winner = no;
+            check++;
+            break;
+        }
+    }
+
+
+    nonce++;
+}
+        }
+
+        LocalTime time_after = LocalTime.now();
+        //считаем разницу во времени
+        synchronized(this) {
+            if (no == winner) {
+                this.tiktok = Math.abs(time_after.getMinute() - time_before.getMinute()) * 60 + Math.abs(time_after.getSecond() - time_before.getSecond());
+
+                return nonceHash;
+            }else{
+                return "null";
+            }
+        }
+
+
+    }
+
+
+    private Boolean validate(String previousblock, String currentblock) {
+        String check = proofOfWork(previousblock);
+        if(check.equals(currentblock)){
+            return true;
+        }else {
+            return false;
+        }
+
+    }
+
+    private String GenerateBlock(String currentid) {
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            /* Applies sha256 to our input */
+            byte[] hash = digest.digest(currentid.getBytes("UTF-8"));
+            StringBuilder hexString = new StringBuilder();
+            for (byte elem: hash) {
+                String hex = Integer.toHexString(0xff & elem);
+                if(hex.length() == 1) hexString.append('0');
+                hexString.append(hex);
+            }
+            return hexString.toString();
+        }
+        catch(Exception e) {
+            throw new RuntimeException(e);
+        }
+
+    }
+
+}

src/blockchain/Main.java

@@ -1,7 +1,19 @@
 package blockchain;
 
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+
 public class Main {
+
     public static void main(String[] args) {
-        System.out.print("Hello world!");
+      int miners_count = 4;
+
+       for (int i = 1; i <=miners_count;  i ++){
+           Thread thread = new Blockchain(i);
+           thread.start();
+       }
+
+
+    }
     }
-}