Fixed some issues, and made things readible from File.

build.gradle

@@ -1,5 +1,6 @@
 plugins {
     id 'java'
+    id 'com.gradleup.shadow' version '9.0.0-beta7'
 }
 
 group = 'me.zacharias'
@@ -10,8 +11,16 @@ repositories {
 }
 
 dependencies {
+    implementation 'com.google.code.gson:gson:2.12.1'
+    implementation("org.jetbrains:annotations:23.1.0")
 }
 
 test {
     useJUnitPlatform()
+}
+
+jar{
+    manifest {
+        attributes 'Main-class': 'me.zacharias.bank.Main'
+    }
 }

src/main/java/me/zacharias/bank/Account.java

@@ -2,21 +2,25 @@ package me.zacharias.bank;
 
 import me.zacharias.bank.transaction.Transaction;
 import me.zacharias.bank.transaction.TransactionType;
+import org.intellij.lang.annotations.MagicConstant;
 
 import java.util.ArrayList;
 import java.util.UUID;
 
-public abstract class Account {
+public class Account {
     ArrayList<Transaction> transactions;
     String name;
     double balance;
     UUID id;
+    @MagicConstant(valuesFromClass = Interests.class)
+    double interestRate;
 
-    public Account(String name, int balance) {
+    public Account(String name, double balance, @MagicConstant(valuesFromClass = Interests.class) double interestRate) {
         this.name = name;
         this.balance = balance;
         transactions = new ArrayList<>();
         id = UUID.randomUUID();
+        this.interestRate = interestRate;
     }
 
     public void WithdrawTransaction(double amount, String description, UUID destination) {
@@ -85,9 +89,13 @@ public abstract class Account {
         return transactions;
     }
     
-    abstract double getInterestRate();
-    
     public double getInterest() {
-        return balance * (1+getInterestRate());
+        return balance * (1+interestRate);
+    }
+
+    public static class Interests
+    {
+        public static final double BANK_ACCOUNT_INTEREST_RATE = 0.001;
+        public static final double SAVINGS_ACCOUNT_INTEREST_RATE = 0.05;
     }
 }

src/main/java/me/zacharias/bank/AccountType.java

@@ -0,0 +1,7 @@
+package me.zacharias.bank;
+
+public enum AccountType {
+    BANK_ACCOUNT,
+    SAVINGS_ACCOUNT,
+    UNKNOWN,
+}

src/main/java/me/zacharias/bank/BankAccount.java

@@ -1,12 +1,12 @@
 package me.zacharias.bank;
 
-public class BankAccount extends Account {
-    public BankAccount(String name, int balance) {
-        super(name, balance);
-    }
+import static me.zacharias.bank.Account.Interests.BANK_ACCOUNT_INTEREST_RATE;
 
-    @Override
-    double getInterestRate() {
-        return 0.001;
+/**
+ * This class only works as a way to have prefilled information, but can be replaced by just calling the {@link Account#Account(String, double, double)} instead
+ */
+public class BankAccount extends Account {
+    public BankAccount(String name, double balance) {
+        super(name, balance, BANK_ACCOUNT_INTEREST_RATE);
     }
 }

src/main/java/me/zacharias/bank/Main.java

@@ -1,5 +1,84 @@
 package me.zacharias.bank;
 
-public class Main {
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 
+import java.io.Console;
+import java.io.File;
+import java.util.UUID;
+
+import static me.zacharias.bank.Utils.*;
+
+public class Main {
+    User user;
+
+    static Gson gson;
+
+    static {
+        GsonBuilder gsonBuilder = new GsonBuilder();
+        //gsonBuilder.registerTypeAdapter(Account.class, new AccountAdapter());
+
+        gson = gsonBuilder.create();
+    }
+
+    public static void main(String[] args) {
+        String user = SHA256("zacharias");
+        File userFile = new File("./users/" + user + ".json");
+
+        if(!userFile.exists()) {
+
+            User u = new User("zacharias");
+            u.createAccount("Konto", 0.0);
+            Account a = u.getAccount("Konto");
+            a.DepositTransaction(104, "Spawnar pängar", UUID.randomUUID());
+
+            String json = gson.toJson(u);
+            try {
+                WriteFile(userFile, Encrypt(json, "pass"));
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        new Main();
+    }
+
+    public Main() {
+
+        Console console = System.console();
+
+        if(console == null) {
+            System.out.println("No console.");
+            //return;
+        }
+
+        String name = "zacharias";//console.readLine("Enter your name: ");
+
+        String userHash = SHA256(name);
+
+        File userFile = new File("./users/" + userHash + ".json");
+
+        if(!userFile.exists()) {
+            System.out.println("User does not exist");
+            return;
+        }
+
+        String password = "pass";//new String(console.readPassword("Enter your password: "));
+
+        String userData;
+
+        try {
+            userData = Decrypt(ReadFile(userFile), password);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+
+        System.out.println(userData);
+
+        user = gson.fromJson(userData, User.class);
+
+        Account a = user.getAccount("Konto");
+        System.out.println(a.getClass().getSimpleName());
+        System.out.println(a.getBalance());
+    }
 }

src/main/java/me/zacharias/bank/SavingsAccount.java

@@ -1,13 +1,13 @@
 package me.zacharias.bank;
 
+import static me.zacharias.bank.Account.Interests.SAVINGS_ACCOUNT_INTEREST_RATE;
+
+/**
+ * This class only works as a way to have prefilled information, but can be replaced by just calling the {@link Account#Account(String, double, double)} instead
+ */
 public class SavingsAccount extends Account{
     
-    public SavingsAccount(String name, int balance) {
-        super(name, balance);
-    }
-    
-    @Override
-    double getInterestRate() {
-        return 0.05;
+    public SavingsAccount(String name, double balance) {
+        super(name, balance, SAVINGS_ACCOUNT_INTEREST_RATE);
     }
 }

src/main/java/me/zacharias/bank/User.java

@@ -6,25 +6,41 @@ import java.util.UUID;
 public class User {
     UUID id;
     String name;
-    String password;
     ArrayList<Account> accounts;
     
-    public User(String name, String password) {
+    public User(String name) {
         this.name = name;
-        this.password = password;
         id = UUID.randomUUID();
         accounts = new ArrayList<>();
     }
     
-    public void createAccount(String name, int balance) {
+    public void createAccount(String name, double balance) {
         Account account = new BankAccount(name, balance);
         accounts.add(account);
     }
     
-    public void createSavingsAccount(String name, int balance) {
+    public void createSavingsAccount(String name, double balance) {
         Account account = new SavingsAccount(name, balance);
         accounts.add(account);
     }
+
+    public Account getAccount(String name) {
+        for (Account account : accounts) {
+            if (account.name.equals(name)) {
+                return account;
+            }
+        }
+        return null;
+    }
+
+    public Account getAccount(UUID id) {
+        for (Account account : accounts) {
+            if (account.id.equals(id)) {
+                return account;
+            }
+        }
+        return null;
+    }
     
     public void deleteAccount(Account account) {
         Account base = null;

src/main/java/me/zacharias/bank/Utils.java

@@ -0,0 +1,133 @@
+package me.zacharias.bank;
+
+import javax.crypto.Cipher;
+import javax.crypto.SecretKey;
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.GCMParameterSpec;
+import javax.crypto.spec.PBEKeySpec;
+import javax.crypto.spec.SecretKeySpec;
+import java.io.*;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.Base64;
+
+public class Utils {
+    public static String SHA256(String input) {
+        MessageDigest sha256 = null;
+        try {
+            sha256 = MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);
+        }
+        byte[] hash = sha256.digest(input.getBytes(StandardCharsets.UTF_8));
+
+        StringBuilder hexString = new StringBuilder();
+        for (byte b : hash) {
+            String hex = Integer.toHexString(0xff & b);
+            if (hex.length() == 1) hexString.append('0');
+            hexString.append(hex);
+        }
+
+        return hexString.toString();
+    }
+
+    private static final int KEY_SIZE = 256;
+    private static final int ITERATIONS = 65536;
+    private static final int SALT_LENGTH = 16;
+    private static final int IV_LENGTH = 12;
+
+    public static String Encrypt(String data, String username) throws Exception {
+        SecureRandom random = new SecureRandom();
+
+        byte[] salt = new byte[SALT_LENGTH];
+        random.nextBytes(salt);
+
+        byte[] iv = new byte[IV_LENGTH];
+        random.nextBytes(iv);
+
+        SecretKey key = deriveKey(username, salt);
+
+        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
+        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
+        cipher.init(Cipher.ENCRYPT_MODE, key, gcmSpec);
+        byte[] encryptedData = cipher.doFinal(data.getBytes());
+
+        byte[] combined = new byte[salt.length + iv.length + encryptedData.length];
+        System.arraycopy(salt, 0, combined, 0, salt.length);
+        System.arraycopy(iv, 0, combined, salt.length, iv.length);
+        System.arraycopy(encryptedData, 0, combined, salt.length + iv.length, encryptedData.length);
+
+        return Base64.getEncoder().encodeToString(combined);
+    }
+
+    public static String Decrypt(String data, String username) throws Exception {
+        byte[] combined = Base64.getDecoder().decode(data);
+
+        // Extract salt, IV, and encrypted data
+        byte[] salt = new byte[SALT_LENGTH];
+        byte[] iv = new byte[IV_LENGTH];
+        byte[] cipherText = new byte[combined.length - SALT_LENGTH - IV_LENGTH];
+
+        System.arraycopy(combined, 0, salt, 0, salt.length);
+        System.arraycopy(combined, salt.length, iv, 0, iv.length);
+        System.arraycopy(combined, salt.length + iv.length, cipherText, 0, cipherText.length);
+
+        SecretKey key = deriveKey(username, salt);
+
+        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
+        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
+        cipher.init(Cipher.DECRYPT_MODE, key, gcmSpec);
+        byte[] decrptedData = cipher.doFinal(cipherText);
+
+        return new String(decrptedData);
+    }
+
+    private static SecretKey deriveKey(String password, byte[] salt) throws Exception {
+        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+        PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), salt, ITERATIONS, KEY_SIZE);
+        return new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
+    }
+
+    public static String ReadFile(File file)
+    {
+        if(!file.exists())
+        {
+            throw new RuntimeException(new FileNotFoundException(file.getPath()+" not found"));
+        }
+
+        try {
+            BufferedReader br = new BufferedReader(new FileReader(file));
+            StringBuilder sb = new StringBuilder();
+            String line;
+            while((line = br.readLine()) != null)
+            {
+                sb.append(line);
+            }
+            return sb.toString();
+        }
+        catch (IOException e)
+        {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static void WriteFile(File file, String data) {
+        if(file.exists())
+        {
+            file.delete();
+        }
+
+        try {
+            file.createNewFile();
+
+            BufferedWriter bw = new BufferedWriter(new FileWriter(file));
+            bw.write(data);
+            bw.close();
+        }catch (IOException e)
+        {
+            throw new RuntimeException(e);
+        }
+    }
+}