Complete Application & Review

Assemble the complete banking application and review all Java concepts applied — the capstone that ties together the entire course.

45 min•By Priygop Team•Last updated: Feb 2026

Concepts Applied

OOP Principles: Encapsulation (private fields + public methods), Inheritance (SavingsAccount extends BankAccount), Polymorphism (calculateInterest() override), Abstraction (BankAccount interface hides complexity)
Collections Applied: ArrayList<Transaction> for ordered transaction history, HashMap<String, BankAccount> for O(1) account lookup, Collections.sort() for sorting accounts by balance
Exception Handling Applied: IllegalArgumentException for validation, FileNotFoundException for missing files, InputMismatchException for invalid user input, custom InsufficientFundsException
File I/O Applied: BufferedReader/PrintWriter for CSV files, try-with-resources for automatic resource cleanup, append mode for transaction logs, directory creation with Files API
Streams Applied: accounts.values().stream().mapToDouble(BankAccount::getBalance).sum() — calculate total bank assets. .filter(a -> a.getBalance() > 10000).count() — count high-value accounts
Formatting Applied: String.format() and System.out.printf() for professional console output — aligned columns, currency formatting with commas, date formatting with SimpleDateFormat

Try It Yourself: Bank Account Class

Try It Yourself: Bank Account ClassJava

Java Editor

✓ ValidTab = 2 spaces

import java.util.ArrayList;

class BankAccount {
    private String owner;
    private double balance;
    private ArrayList<String> history;

    public BankAccount(String owner, double initial) {
        this.owner = owner;
        this.balance = initial;
        this.history = new ArrayList<>();
        history.add("Account opened: $" + initial);
    }

    public void deposit(double amount) {
        balance += amount;
        history.add("Deposit: +$" + amount);
        System.out.println("Deposited $" + amount);
    }

    public boolean withdraw(double amount) {
        if (amount > balance) {
            System.out.println("Insufficient funds!");
            return false;
        }
        balance -= amount;
        history.add("Withdraw: -$" + amount);
        System.out.println("Withdrew $" + amount);
        return true;
    }

    public void printSummary() {
        System.out.println("
Account: " + owner);
        System.out.println("Balance: $" + balance);
        System.out.println("History:");
        for (String h : history) System.out.println("  " + h);
    }

    public static void main(String[] args) {
        BankAccount acc = new BankAccount("Alice", 1000);
        acc.deposit(500);
        acc.withdraw(200);
        acc.withdraw(2000);
        acc.printSummary();
    }
}

import java.util.ArrayList;

class BankAccount {
    private String owner;
    private double balance;
    private ArrayList<String> history;

public BankAccount(String owner, double initial) {
        this.owner = owner;
        this.balance = initial;
        this.history = new ArrayList<>();
        history.add("Account opened: $" + initial);
    }

public void deposit(double amount) {
        balance += amount;
        history.add("Deposit: +$" + amount);
        System.out.println("Deposited $" + amount);
    }

public boolean withdraw(double amount) {
        if (amount > balance) {
            System.out.println("Insufficient funds!");
            return false;
        }
        balance -= amount;
        history.add("Withdraw: -$" + amount);
        System.out.println("Withdrew $" + amount);
        return true;
    }

public void printSummary() {
        System.out.println("
Account: " + owner);
        System.out.println("Balance: $" + balance);
        System.out.println("History:");
        for (String h : history) System.out.println("  " + h);
    }

public static void main(String[] args) {
        BankAccount acc = new BankAccount("Alice", 1000);
        acc.deposit(500);
        acc.withdraw(200);
        acc.withdraw(2000);
        acc.printSummary();
    }
}

Output

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Edit the code on the left, then click Run

Java|47 lines|1315 chars|✓ Valid syntax

UTF-8

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