銀行のATMシステムにおける残高照会、入金、出金、振込の操作をJavaで実装し、Oracle Databaseと連携するサンプルプログラムを以下に示します。この例では、JavaのJDBC（Java Database Connectivity）を使用してOracle Databaseと接続し、基本的なATM操作を実装します。
### 1. Oracle Databaseのセットアップ
まず、Oracle Databaseに必要なテーブルを作成します。以下は、ユーザー情報と取引履歴を管理するためのテーブルの例です。
```sql
CREATE TABLE users (
user_id NUMBER PRIMARY KEY,
name VARCHAR2(100),
balance NUMBER(10, 2) DEFAULT 0
);
CREATE TABLE transactions (
transaction_id NUMBER PRIMARY KEY,
user_id NUMBER,
transaction_type VARCHAR2(10),
amount NUMBER(10, 2),
transaction_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
FOREIGN KEY (user_id) REFERENCES users(user_id)
);
```
### 2. Javaプログラム
次に、Javaプログラムを作成します。このプログラムは、ユーザー認証、残高照会、入金、出金、振込の操作を実装します。
#### 2.1. JDBC接続の設定
```java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class ATMSystem {
private static final String URL = "jdbc:oracle:thin:@localhost:1521:xe";
private static final String USER = "your_username";
private static final String PASSWORD = "your_password";
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(URL, USER, PASSWORD);
}
}
```
#### 2.2. ユーザー認証
```java
public class UserAuthentication {
public static boolean authenticateUser(int userId, String password) throws SQLException {
String query = "SELECT * FROM users WHERE user_id = ? AND password = ?";
try (Connection conn = ATMSystem.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setInt(1, userId);
pstmt.setString(2, password);
try (ResultSet rs = pstmt.executeQuery()) {
return rs.next();
}
}
}
}
```
#### 2.3. 残高照会
```java
public class BalanceInquiry {
public static double checkBalance(int userId) throws SQLException {
String query = "SELECT balance FROM users WHERE user_id = ?";
try (Connection conn = ATMSystem.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setInt(1, userId);
try (ResultSet rs = pstmt.executeQuery()) {
if (rs.next()) {
return rs.getDouble("balance");
}
}
}
return 0.0;
}
}
```
#### 2.4. 入金
```java
public class Deposit {
public static void deposit(int userId, double amount) throws SQLException {
String query = "UPDATE users SET balance = balance + ? WHERE user_id = ?";
try (Connection conn = ATMSystem.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setDouble(1, amount);
pstmt.setInt(2, userId);
pstmt.executeUpdate();
insertTransaction(userId, "DEPOSIT", amount);
}
}
private static void insertTransaction(int userId, String transactionType, double amount) throws SQLException {
String query = "INSERT INTO transactions (transaction_id, user_id, transaction_type, amount) VALUES (transactions_seq.NEXTVAL, ?, ?, ?)";
try (Connection conn = ATMSystem.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setInt(1, userId);
pstmt.setString(2, transactionType);
pstmt.setDouble(3, amount);
pstmt.executeUpdate();
}
}
}
```
#### 2.5. 出金
```java
public class Withdraw {
public static void withdraw(int userId, double amount) throws SQLException {
String query = "UPDATE users SET balance = balance - ? WHERE user_id = ? AND balance >= ?";
try (Connection conn = ATMSystem.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setDouble(1, amount);
pstmt.setInt(2, userId);
pstmt.setDouble(3, amount);
int rowsAffected = pstmt.executeUpdate();
if (rowsAffected > 0) {
insertTransaction(userId, "WITHDRAW", amount);
} else {
System.out.println("不足金額です。");
}
}
}
}
```
#### 2.6. 振込
```java
public class Transfer {
public static void transfer(int fromUserId, int toUserId, double amount) throws SQLException {
String query = "UPDATE users SET balance = balance - ? WHERE user_id = ? AND balance >= ?";
try (Connection conn = ATMSystem.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setDouble(1, amount);
pstmt.setInt(2, fromUserId);
pstmt.setDouble(3, amount);
int rowsAffected = pstmt.executeUpdate();
if (rowsAffected > 0) {
query = "UPDATE users SET balance = balance + ? WHERE user_id = ?";
try (PreparedStatement pstmt2 = conn.prepareStatement(query)) {
pstmt2.setDouble(1, amount);
pstmt2.setInt(2, toUserId);
pstmt2.executeUpdate();
insertTransaction(fromUserId, "TRANSFER", -amount);
insertTransaction(toUserId, "TRANSFER", amount);
}
} else {
System.out.println("不足金額です。");
}
}
}
}
```
### 3. フロントエンドのGUI
Java Swingを使用して簡単なGUIを作成します。このGUIは、ユーザーが残高を照会したり、入金や出金、振込を行ったりするためのインターフェースを提供します。
```java
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.SQLException;
public class ATMGUI extends JFrame {
private JTextField userIdField;
private JTextField amountField;
private JTextField toUserIdField;
private JTextArea outputArea;
public ATMGUI() {
setTitle("ATM System");
setSize(400, 300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(6, 2));
userIdField = new JTextField();
amountField = new JTextField();
toUserIdField = new JTextField();
outputArea = new JTextArea();
outputArea.setEditable(false);
panel.add(new JLabel("User ID:"));
panel.add(userIdField);
panel.add(new JLabel("Amount:"));
panel.add(amountField);
panel.add(new JLabel("To User ID:"));
panel.add(toUserIdField);
JButton checkBalanceButton = new JButton("Check Balance");
JButton depositButton = new JButton("Deposit");
JButton withdrawButton = new JButton("Withdraw");
JButton transferButton = new JButton("Transfer");
checkBalanceButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try {
int userId = Integer.parseInt(userIdField.getText());
double balance = BalanceInquiry.checkBalance(userId);
outputArea.append("Balance: " + balance + "\n");
} catch (SQLException | NumberFormatException ex) {
outputArea.append("Error: " + ex.getMessage() + "\n");
}
}
});
depositButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try {
int userId = Integer.parseInt(userIdField.getText());
double amount = Double.parseDouble(amountField.getText());
Deposit.deposit(userId, amount);
outputArea.append("Deposited: " + amount + "\n");
} catch (SQLException | NumberFormatException ex) {
outputArea.append("Error: " + ex.getMessage() + "\n");
}
}
});
withdrawButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try {
int userId = Integer.parseInt(userIdField.getText());
double amount = Double.parseDouble(amountField.getText());
Withdraw.withdraw(userId, amount);
outputArea.append("Withdrew: " + amount + "\n");
} catch (SQLException | NumberFormatException ex) {
outputArea.append("Error: " + ex.getMessage() + "\n");
}
}
});
transferButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try {
int fromUserId = Integer.parseInt(userIdField.getText());
int toUserId = Integer.parseInt(toUserIdField.getText());
double amount = Double.parseDouble(amountField.getText());
Transfer.transfer(fromUserId, toUserId, amount);
outputArea.append("Transferred: " + amount + " to User ID: " + toUserId + "\n");
} catch (SQLException | NumberFormatException ex) {
outputArea.append("Error: " + ex.getMessage() + "\n");
}
}
});
panel.add(checkBalanceButton);
panel.add(depositButton);
panel.add(withdrawButton);
panel.add(transferButton);
add(new JScrollPane(outputArea), BorderLayout.SOUTH);
add(panel, BorderLayout.NORTH);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new ATMGUI().setVisible(true);
}
});
}
}
```
このプログラムは、Java Swingを使用して簡単なATMシステムのGUIを作成し、Oracle Databaseと連携して基本的なATM操作を実装しています。ユーザーはこのインターフェースを通じて、残高照会、入金、出金、振込を行うことができます。
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