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Utoljára aktív 1741791789

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MediciBankingSystem.java(fájl létrehozva)

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1 + /**
2 +
3 + This Java implementation showcases the core principles of double-entry accounting, using ducats as
4 + the currency in honor of the Medici banking dynasty. Here's what the code demonstrates:
5 +
6 + 1. **The Fundamental Principle**: Every transaction affects at least two accounts
7 + (the double-entry principle), and the sum of debits must always equal the sum of credits.
8 +
9 + 2. **Five Main Account Types**:
10 + - Assets: Resources owned by the business
11 + - Liabilities: Debts owed by the business
12 + - Equity: Owner's interest in the business
13 + - Revenue: Income earned by the business
14 + - Expenses: Costs incurred by the business
15 +
16 + 3. **Account Balance Rules**:
17 + - Assets and Expenses: Increased by debits, decreased by credits
18 + - Liabilities, Equity, and Revenue: Increased by credits, decreased by debits
19 +
20 + 4. **Key Financial Reports**:
21 + - Trial Balance: Verifies that total debits equal total credits
22 + - Balance Sheet: Shows Assets = Liabilities + Equity
23 + - Income Statement: Shows Revenue - Expenses = Net Income
24 +
25 + The example simulates transactions for the Medici Bank in the year 1397,
26 + including initial capitalization, loans with interest (a key banking activity),
27 + property acquisition, and operating expenses.
28 +
29 + */
30 + import java.math.BigDecimal;
31 + import java.math.RoundingMode;
32 + import java.time.LocalDate;
33 + import java.util.*;
34 +
35 + /**
36 + * A double-entry accounting system implementation inspired by the
37 + * Florentine banking practices of the deMedici family.
38 + */
39 + public class MediciBankingSystem {
40 +
41 + public static void main(String[] args) {
42 + // Create a new ledger for our banking operations
43 + Ledger mediciLedger = new Ledger("Medici Family Bank");
44 +
45 + // Define our chart of accounts
46 + Account cash = mediciLedger.createAccount("Cash", AccountType.ASSET);
47 + Account accounts_receivable = mediciLedger.createAccount("Accounts Receivable", AccountType.ASSET);
48 + Account inventory = mediciLedger.createAccount("Inventory", AccountType.ASSET);
49 + Account land = mediciLedger.createAccount("Land", AccountType.ASSET);
50 +
51 + Account accounts_payable = mediciLedger.createAccount("Accounts Payable", AccountType.LIABILITY);
52 + Account loans = mediciLedger.createAccount("Loans", AccountType.LIABILITY);
53 +
54 + Account capital = mediciLedger.createAccount("Owner's Capital", AccountType.EQUITY);
55 + Account retained_earnings = mediciLedger.createAccount("Retained Earnings", AccountType.EQUITY);
56 +
57 + Account revenue = mediciLedger.createAccount("Revenue", AccountType.REVENUE);
58 + Account interest_income = mediciLedger.createAccount("Interest Income", AccountType.REVENUE);
59 +
60 + Account expenses = mediciLedger.createAccount("Expenses", AccountType.EXPENSE);
61 + Account wages = mediciLedger.createAccount("Wages", AccountType.EXPENSE);
62 +
63 + // Starting our banking operations with initial capital
64 + System.out.println("=== STARTING THE MEDICI BANK ===");
65 + mediciLedger.recordTransaction(
66 + LocalDate.of(1397, 1, 1),
67 + "Initial investment from Giovanni de' Medici",
68 + new TransactionEntry(cash, new BigDecimal("10000.00")),
69 + new TransactionEntry(capital, new BigDecimal("10000.00"))
70 + );
71 +
72 + // Recording a loan to a wool merchant
73 + mediciLedger.recordTransaction(
74 + LocalDate.of(1397, 2, 15),
75 + "Loan to Wool Merchant",
76 + new TransactionEntry(accounts_receivable, new BigDecimal("2000.00")),
77 + new TransactionEntry(cash, new BigDecimal("2000.00"))
78 + );
79 +
80 + // Receiving partial payment with interest
81 + mediciLedger.recordTransaction(
82 + LocalDate.of(1397, 8, 10),
83 + "Partial loan repayment from Wool Merchant with interest",
84 + new TransactionEntry(cash, new BigDecimal("1200.00")),
85 + new TransactionEntry(accounts_receivable, new BigDecimal("1000.00")),
86 + new TransactionEntry(interest_income, new BigDecimal("200.00"))
87 + );
88 +
89 + // Purchasing land for a new banking house
90 + mediciLedger.recordTransaction(
91 + LocalDate.of(1397, 9, 5),
92 + "Purchase of land for new Medici banking house",
93 + new TransactionEntry(land, new BigDecimal("3000.00")),
94 + new TransactionEntry(cash, new BigDecimal("3000.00"))
95 + );
96 +
97 + // Paying wages to bank employees
98 + mediciLedger.recordTransaction(
99 + LocalDate.of(1397, 12, 1),
100 + "Quarterly wages for bank employees",
101 + new TransactionEntry(wages, new BigDecimal("800.00")),
102 + new TransactionEntry(cash, new BigDecimal("800.00"))
103 + );
104 +
105 + // Print the trial balance to verify our accounting is balanced
106 + System.out.println("\n=== MEDICI BANK TRIAL BALANCE (Year 1397) ===");
107 + mediciLedger.printTrialBalance();
108 +
109 + // Print the balance sheet
110 + System.out.println("\n=== MEDICI BANK BALANCE SHEET (Year 1397) ===");
111 + mediciLedger.printBalanceSheet();
112 +
113 + // Print the income statement
114 + System.out.println("\n=== MEDICI BANK INCOME STATEMENT (Year 1397) ===");
115 + mediciLedger.printIncomeStatement();
116 + }
117 + }
118 +
119 + /**
120 + * Represents a financial account in the double-entry system
121 + */
122 + class Account {
123 + private String name;
124 + private AccountType type;
125 + private BigDecimal balance;
126 +
127 + public Account(String name, AccountType type) {
128 + this.name = name;
129 + this.type = type;
130 + this.balance = BigDecimal.ZERO;
131 + }
132 +
133 + public String getName() {
134 + return name;
135 + }
136 +
137 + public AccountType getType() {
138 + return type;
139 + }
140 +
141 + public BigDecimal getBalance() {
142 + return balance;
143 + }
144 +
145 + /**
146 + * Debits increase ASSET and EXPENSE accounts
147 + * Debits decrease LIABILITY, EQUITY, and REVENUE accounts
148 + */
149 + public void debit(BigDecimal amount) {
150 + if (type == AccountType.ASSET || type == AccountType.EXPENSE) {
151 + balance = balance.add(amount);
152 + } else {
153 + balance = balance.subtract(amount);
154 + }
155 + }
156 +
157 + /**
158 + * Credits decrease ASSET and EXPENSE accounts
159 + * Credits increase LIABILITY, EQUITY, and REVENUE accounts
160 + */
161 + public void credit(BigDecimal amount) {
162 + if (type == AccountType.ASSET || type == AccountType.EXPENSE) {
163 + balance = balance.subtract(amount);
164 + } else {
165 + balance = balance.add(amount);
166 + }
167 + }
168 +
169 + @Override
170 + public String toString() {
171 + return name + " (" + type + "): " + balance + " ducats";
172 + }
173 + }
174 +
175 + /**
176 + * The different types of accounts in double-entry accounting
177 + */
178 + enum AccountType {
179 + ASSET, // Resources owned by the business
180 + LIABILITY, // Debts owed by the business
181 + EQUITY, // Owner's interest in the business
182 + REVENUE, // Income earned by the business
183 + EXPENSE // Costs incurred by the business
184 + }
185 +
186 + /**
187 + * Represents a single entry in a transaction
188 + */
189 + class TransactionEntry {
190 + private Account account;
191 + private BigDecimal amount;
192 +
193 + public TransactionEntry(Account account, BigDecimal amount) {
194 + this.account = account;
195 + this.amount = amount;
196 + }
197 +
198 + public Account getAccount() {
199 + return account;
200 + }
201 +
202 + public BigDecimal getAmount() {
203 + return amount;
204 + }
205 + }
206 +
207 + /**
208 + * Represents a complete financial transaction in the double-entry system
209 + */
210 + class Transaction {
211 + private String description;
212 + private LocalDate date;
213 + private List<TransactionEntry> debits;
214 + private List<TransactionEntry> credits;
215 +
216 + public Transaction(LocalDate date, String description) {
217 + this.date = date;
218 + this.description = description;
219 + this.debits = new ArrayList<>();
220 + this.credits = new ArrayList<>();
221 + }
222 +
223 + public void addDebit(TransactionEntry entry) {
224 + debits.add(entry);
225 + }
226 +
227 + public void addCredit(TransactionEntry entry) {
228 + credits.add(entry);
229 + }
230 +
231 + public boolean isBalanced() {
232 + BigDecimal totalDebits = debits.stream()
233 + .map(TransactionEntry::getAmount)
234 + .reduce(BigDecimal.ZERO, BigDecimal::add);
235 +
236 + BigDecimal totalCredits = credits.stream()
237 + .map(TransactionEntry::getAmount)
238 + .reduce(BigDecimal.ZERO, BigDecimal::add);
239 +
240 + return totalDebits.compareTo(totalCredits) == 0;
241 + }
242 +
243 + public void post() {
244 + // Apply all debits
245 + for (TransactionEntry entry : debits) {
246 + entry.getAccount().debit(entry.getAmount());
247 + }
248 +
249 + // Apply all credits
250 + for (TransactionEntry entry : credits) {
251 + entry.getAccount().credit(entry.getAmount());
252 + }
253 + }
254 +
255 + @Override
256 + public String toString() {
257 + StringBuilder sb = new StringBuilder();
258 + sb.append("Transaction: ").append(date).append(" - ").append(description).append("\n");
259 +
260 + sb.append(" Debits:\n");
261 + for (TransactionEntry entry : debits) {
262 + sb.append(" ").append(entry.getAccount().getName())
263 + .append(": ").append(entry.getAmount()).append(" ducats\n");
264 + }
265 +
266 + sb.append(" Credits:\n");
267 + for (TransactionEntry entry : credits) {
268 + sb.append(" ").append(entry.getAccount().getName())
269 + .append(": ").append(entry.getAmount()).append(" ducats\n");
270 + }
271 +
272 + return sb.toString();
273 + }
274 + }
275 +
276 + /**
277 + * The main ledger that keeps track of all accounts and transactions
278 + */
279 + class Ledger {
280 + private String name;
281 + private List<Account> accounts;
282 + private List<Transaction> transactions;
283 +
284 + public Ledger(String name) {
285 + this.name = name;
286 + this.accounts = new ArrayList<>();
287 + this.transactions = new ArrayList<>();
288 + }
289 +
290 + public Account createAccount(String name, AccountType type) {
291 + Account account = new Account(name, type);
292 + accounts.add(account);
293 + return account;
294 + }
295 +
296 + /**
297 + * Records a transaction with any number of debits and credits,
298 + * ensuring that debits = credits (the fundamental principle of double-entry)
299 + */
300 + public void recordTransaction(LocalDate date, String description,
301 + TransactionEntry... entries) {
302 + Transaction transaction = new Transaction(date, description);
303 +
304 + // Separate entries into debits and credits based on account type
305 + for (TransactionEntry entry : entries) {
306 + Account account = entry.getAccount();
307 + AccountType type = account.getType();
308 +
309 + // For asset and expense accounts, positive amounts are debits
310 + // For liability, equity, and revenue accounts, positive amounts are credits
311 + if (type == AccountType.ASSET || type == AccountType.EXPENSE) {
312 + if (entry.getAmount().compareTo(BigDecimal.ZERO) >= 0) {
313 + transaction.addDebit(entry);
314 + } else {
315 + // Negative amount means we're crediting the account
316 + transaction.addCredit(new TransactionEntry(
317 + account, entry.getAmount().abs()));
318 + }
319 + } else {
320 + if (entry.getAmount().compareTo(BigDecimal.ZERO) >= 0) {
321 + transaction.addCredit(entry);
322 + } else {
323 + // Negative amount means we're debiting the account
324 + transaction.addDebit(new TransactionEntry(
325 + account, entry.getAmount().abs()));
326 + }
327 + }
328 + }
329 +
330 + // Verify that the transaction is balanced
331 + if (!transaction.isBalanced()) {
332 + throw new IllegalArgumentException("Transaction is not balanced: debits must equal credits");
333 + }
334 +
335 + // Post the transaction to update account balances
336 + transaction.post();
337 +
338 + // Record the transaction in the ledger
339 + transactions.add(transaction);
340 + System.out.println(transaction);
341 + }
342 +
343 + /**
344 + * Prints a trial balance to verify that debits = credits across all accounts
345 + */
346 + public void printTrialBalance() {
347 + BigDecimal totalDebits = BigDecimal.ZERO;
348 + BigDecimal totalCredits = BigDecimal.ZERO;
349 +
350 + System.out.printf("%-30s %-15s %-15s%n", "Account", "Debit (Ducats)", "Credit (Ducats)");
351 + System.out.println("-".repeat(60));
352 +
353 + for (Account account : accounts) {
354 + BigDecimal balance = account.getBalance();
355 +
356 + // For the trial balance, we show positive balances in their normal position
357 + // Assets and Expenses with positive balances are shown as debits
358 + // Liabilities, Equity, and Revenue with positive balances are shown as credits
359 + if (account.getType() == AccountType.ASSET ||
360 + account.getType() == AccountType.EXPENSE) {
361 + if (balance.compareTo(BigDecimal.ZERO) > 0) {
362 + System.out.printf("%-30s %-15s %-15s%n",
363 + account.getName(), balance.setScale(2, RoundingMode.HALF_UP), "");
364 + totalDebits = totalDebits.add(balance);
365 + } else if (balance.compareTo(BigDecimal.ZERO) < 0) {
366 + System.out.printf("%-30s %-15s %-15s%n",
367 + account.getName(), "", balance.abs().setScale(2, RoundingMode.HALF_UP));
368 + totalCredits = totalCredits.add(balance.abs());
369 + }
370 + } else {
371 + if (balance.compareTo(BigDecimal.ZERO) > 0) {
372 + System.out.printf("%-30s %-15s %-15s%n",
373 + account.getName(), "", balance.setScale(2, RoundingMode.HALF_UP));
374 + totalCredits = totalCredits.add(balance);
375 + } else if (balance.compareTo(BigDecimal.ZERO) < 0) {
376 + System.out.printf("%-30s %-15s %-15s%n",
377 + account.getName(), balance.abs().setScale(2, RoundingMode.HALF_UP), "");
378 + totalDebits = totalDebits.add(balance.abs());
379 + }
380 + }
381 + }
382 +
383 + System.out.println("-".repeat(60));
384 + System.out.printf("%-30s %-15s %-15s%n",
385 + "TOTAL", totalDebits.setScale(2, RoundingMode.HALF_UP),
386 + totalCredits.setScale(2, RoundingMode.HALF_UP));
387 +
388 + if (totalDebits.compareTo(totalCredits) == 0) {
389 + System.out.println("\nThe books are balanced! ✓");
390 + } else {
391 + System.out.println("\nWARNING: The books are NOT balanced! ✗");
392 + }
393 + }
394 +
395 + /**
396 + * Prints a balance sheet (Assets = Liabilities + Equity)
397 + */
398 + public void printBalanceSheet() {
399 + BigDecimal totalAssets = BigDecimal.ZERO;
400 + BigDecimal totalLiabilities = BigDecimal.ZERO;
401 + BigDecimal totalEquity = BigDecimal.ZERO;
402 +
403 + // Print Assets
404 + System.out.println("ASSETS");
405 + System.out.println("-".repeat(40));
406 + for (Account account : accounts) {
407 + if (account.getType() == AccountType.ASSET && account.getBalance().compareTo(BigDecimal.ZERO) != 0) {
408 + System.out.printf("%-30s %10s%n",
409 + account.getName(), account.getBalance().setScale(2, RoundingMode.HALF_UP));
410 + totalAssets = totalAssets.add(account.getBalance());
411 + }
412 + }
413 + System.out.println("-".repeat(40));
414 + System.out.printf("%-30s %10s%n", "TOTAL ASSETS", totalAssets.setScale(2, RoundingMode.HALF_UP));
415 + System.out.println();
416 +
417 + // Print Liabilities
418 + System.out.println("LIABILITIES");
419 + System.out.println("-".repeat(40));
420 + for (Account account : accounts) {
421 + if (account.getType() == AccountType.LIABILITY && account.getBalance().compareTo(BigDecimal.ZERO) != 0) {
422 + System.out.printf("%-30s %10s%n",
423 + account.getName(), account.getBalance().setScale(2, RoundingMode.HALF_UP));
424 + totalLiabilities = totalLiabilities.add(account.getBalance());
425 + }
426 + }
427 + System.out.println("-".repeat(40));
428 + System.out.printf("%-30s %10s%n", "TOTAL LIABILITIES", totalLiabilities.setScale(2, RoundingMode.HALF_UP));
429 + System.out.println();
430 +
431 + // Print Equity
432 + System.out.println("EQUITY");
433 + System.out.println("-".repeat(40));
434 + for (Account account : accounts) {
435 + if (account.getType() == AccountType.EQUITY && account.getBalance().compareTo(BigDecimal.ZERO) != 0) {
436 + System.out.printf("%-30s %10s%n",
437 + account.getName(), account.getBalance().setScale(2, RoundingMode.HALF_UP));
438 + totalEquity = totalEquity.add(account.getBalance());
439 + }
440 + }
441 + System.out.println("-".repeat(40));
442 + System.out.printf("%-30s %10s%n", "TOTAL EQUITY", totalEquity.setScale(2, RoundingMode.HALF_UP));
443 + System.out.println();
444 +
445 + // Verify the accounting equation: Assets = Liabilities + Equity
446 + System.out.println("ACCOUNTING EQUATION");
447 + System.out.println("-".repeat(40));
448 + System.out.printf("%-30s %10s%n", "Total Assets", totalAssets.setScale(2, RoundingMode.HALF_UP));
449 + System.out.printf("%-30s %10s%n", "Total Liabilities + Equity",
450 + totalLiabilities.add(totalEquity).setScale(2, RoundingMode.HALF_UP));
451 +
452 + if (totalAssets.compareTo(totalLiabilities.add(totalEquity)) == 0) {
453 + System.out.println("\nThe accounting equation is balanced! ✓");
454 + } else {
455 + System.out.println("\nWARNING: The accounting equation is NOT balanced! ✗");
456 + }
457 + }
458 +
459 + /**
460 + * Prints an income statement (Revenue - Expenses = Net Income)
461 + */
462 + public void printIncomeStatement() {
463 + BigDecimal totalRevenue = BigDecimal.ZERO;
464 + BigDecimal totalExpenses = BigDecimal.ZERO;
465 +
466 + // Print Revenue
467 + System.out.println("REVENUE");
468 + System.out.println("-".repeat(40));
469 + for (Account account : accounts) {
470 + if (account.getType() == AccountType.REVENUE && account.getBalance().compareTo(BigDecimal.ZERO) != 0) {
471 + System.out.printf("%-30s %10s%n",
472 + account.getName(), account.getBalance().setScale(2, RoundingMode.HALF_UP));
473 + totalRevenue = totalRevenue.add(account.getBalance());
474 + }
475 + }
476 + System.out.println("-".repeat(40));
477 + System.out.printf("%-30s %10s%n", "TOTAL REVENUE", totalRevenue.setScale(2, RoundingMode.HALF_UP));
478 + System.out.println();
479 +
480 + // Print Expenses
481 + System.out.println("EXPENSES");
482 + System.out.println("-".repeat(40));
483 + for (Account account : accounts) {
484 + if (account.getType() == AccountType.EXPENSE && account.getBalance().compareTo(BigDecimal.ZERO) != 0) {
485 + System.out.printf("%-30s %10s%n",
486 + account.getName(), account.getBalance().setScale(2, RoundingMode.HALF_UP));
487 + totalExpenses = totalExpenses.add(account.getBalance());
488 + }
489 + }
490 + System.out.println("-".repeat(40));
491 + System.out.printf("%-30s %10s%n", "TOTAL EXPENSES", totalExpenses.setScale(2, RoundingMode.HALF_UP));
492 + System.out.println();
493 +
494 + // Calculate Net Income
495 + BigDecimal netIncome = totalRevenue.subtract(totalExpenses);
496 + System.out.println("SUMMARY");
497 + System.out.println("-".repeat(40));
498 + System.out.printf("%-30s %10s%n", "Total Revenue", totalRevenue.setScale(2, RoundingMode.HALF_UP));
499 + System.out.printf("%-30s %10s%n", "Total Expenses", totalExpenses.setScale(2, RoundingMode.HALF_UP));
500 + System.out.println("-".repeat(40));
501 + System.out.printf("%-30s %10s%n", "NET INCOME", netIncome.setScale(2, RoundingMode.HALF_UP));
502 + }
503 + }
504 +
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