Add Java Code

Author: AdityaPandey-DEV

AlternateList_Q23.java

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+/**
+ * AlternateList_Q23.java
+ * 
+ * This program demonstrates a method that accepts two Lists of integers
+ * and returns a new List containing alternating elements from the two lists.
+ */
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class AlternateList_Q23 {
+    public static void main(String[] args) {
+        // Test case 1: Lists of equal length
+        List<Integer> list1 = Arrays.asList(1, 2, 3, 4, 5);
+        List<Integer> list2 = Arrays.asList(6, 7, 8, 9, 10);
+        
+        List<Integer> result1 = alternate(list1, list2);
+        System.out.println("List 1: " + list1);
+        System.out.println("List 2: " + list2);
+        System.out.println("Alternating result: " + result1);
+        // Expected output: [1, 6, 2, 7, 3, 8, 4, 9, 5, 10]
+        
+        // Test case 2: First list is longer
+        List<Integer> list3 = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
+        List<Integer> list4 = Arrays.asList(8, 9, 10);
+        
+        List<Integer> result2 = alternate(list3, list4);
+        System.out.println("\nList 3: " + list3);
+        System.out.println("List 4: " + list4);
+        System.out.println("Alternating result: " + result2);
+        // Expected output: [1, 8, 2, 9, 3, 10, 4, 5, 6, 7]
+        
+        // Test case 3: Second list is longer
+        List<Integer> list5 = Arrays.asList(1, 2, 3, 4, 5);
+        List<Integer> list6 = Arrays.asList(6, 7, 8, 9, 10, 11, 12);
+        
+        List<Integer> result3 = alternate(list5, list6);
+        System.out.println("\nList 5: " + list5);
+        System.out.println("List 6: " + list6);
+        System.out.println("Alternating result: " + result3);
+        // Expected output: [1, 6, 2, 7, 3, 8, 4, 9, 5, 10, 11, 12]
+    }
+    
+    /**
+     * Returns a new List containing alternating elements from the two input lists.
+     * If the lists do not contain the same number of elements, the remaining elements
+     * from the longer list are placed consecutively at the end.
+     * 
+     * @param list1 the first List of integers
+     * @param list2 the second List of integers
+     * @return a new List containing alternating elements from the two input lists
+     */
+    public static List<Integer> alternate(List<Integer> list1, List<Integer> list2) {
+        List<Integer> result = new ArrayList<>();
+        
+        // Determine the minimum length of the two lists
+        int minLength = Math.min(list1.size(), list2.size());
+        
+        // Add alternating elements from both lists
+        for (int i = 0; i < minLength; i++) {
+            result.add(list1.get(i));
+            result.add(list2.get(i));
+        }
+        
+        // Add remaining elements from list1 if it's longer
+        for (int i = minLength; i < list1.size(); i++) {
+            result.add(list1.get(i));
+        }
+        
+        // Add remaining elements from list2 if it's longer
+        for (int i = minLength; i < list2.size(); i++) {
+            result.add(list2.get(i));
+        }
+        
+        return result;
+    }
+} 

EmployeeDatabase_Q26.java

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+/**
+ * EmployeeDatabase_Q26.java
+ * 
+ * This program demonstrates JDBC connectivity with a database to store and retrieve
+ * employee records. It includes a GUI for data entry and display.
+ * 
+ * Note: This program requires the appropriate JDBC driver for MySQL or PostgreSQL
+ * to be in the classpath.
+ */
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.*;
+import java.sql.*;
+import javax.swing.table.DefaultTableModel;
+
+public class EmployeeDatabase_Q26 extends JFrame {
+    // JDBC Database URL, Username, and Password
+    // Change these values according to your database setup
+    private static final String DB_URL = "jdbc:mysql://localhost:3306/employee_db";
+    private static final String DB_USER = "root";
+    private static final String DB_PASSWORD = "password";
+    
+    // UI Components
+    private JTextField nameField;
+    private JTextField codeField;
+    private JTextField designationField;
+    private JTextField salaryField;
+    private JButton saveButton;
+    private JButton viewButton;
+    private JButton clearButton;
+    private JTable employeeTable;
+    private DefaultTableModel tableModel;
+    
+    public EmployeeDatabase_Q26() {
+        // Set up the frame
+        super("Employee Database");
+        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        setSize(600, 500);
+        setLocationRelativeTo(null);
+        
+        // Create the main panel with a border layout
+        JPanel mainPanel = new JPanel(new BorderLayout(10, 10));
+        mainPanel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
+        
+        // Create the input form panel
+        JPanel formPanel = createFormPanel();
+        mainPanel.add(formPanel, BorderLayout.NORTH);
+        
+        // Create the table panel
+        JPanel tablePanel = createTablePanel();
+        mainPanel.add(tablePanel, BorderLayout.CENTER);
+        
+        // Set the content pane
+        setContentPane(mainPanel);
+        
+        // Initialize the database
+        initializeDatabase();
+    }
+    
+    private JPanel createFormPanel() {
+        JPanel panel = new JPanel(new GridBagLayout());
+        panel.setBorder(BorderFactory.createTitledBorder("Employee Information"));
+        
+        GridBagConstraints gbc = new GridBagConstraints();
+        gbc.fill = GridBagConstraints.HORIZONTAL;
+        gbc.insets = new Insets(5, 5, 5, 5);
+        
+        // Name field
+        gbc.gridx = 0;
+        gbc.gridy = 0;
+        panel.add(new JLabel("Name:"), gbc);
+        
+        gbc.gridx = 1;
+        gbc.gridy = 0;
+        gbc.weightx = 1.0;
+        nameField = new JTextField(20);
+        panel.add(nameField, gbc);
+        
+        // Code field
+        gbc.gridx = 0;
+        gbc.gridy = 1;
+        gbc.weightx = 0.0;
+        panel.add(new JLabel("Code:"), gbc);
+        
+        gbc.gridx = 1;
+        gbc.gridy = 1;
+        gbc.weightx = 1.0;
+        codeField = new JTextField(10);
+        panel.add(codeField, gbc);
+        
+        // Designation field
+        gbc.gridx = 0;
+        gbc.gridy = 2;
+        gbc.weightx = 0.0;
+        panel.add(new JLabel("Designation:"), gbc);
+        
+        gbc.gridx = 1;
+        gbc.gridy = 2;
+        gbc.weightx = 1.0;
+        designationField = new JTextField(20);
+        panel.add(designationField, gbc);
+        
+        // Salary field
+        gbc.gridx = 0;
+        gbc.gridy = 3;
+        gbc.weightx = 0.0;
+        panel.add(new JLabel("Salary:"), gbc);
+        
+        gbc.gridx = 1;
+        gbc.gridy = 3;
+        gbc.weightx = 1.0;
+        salaryField = new JTextField(10);
+        panel.add(salaryField, gbc);
+        
+        // Button panel
+        JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.CENTER, 10, 0));
+        
+        saveButton = new JButton("Save");
+        saveButton.addActionListener(e -> saveEmployee());
+        
+        viewButton = new JButton("View All");
+        viewButton.addActionListener(e -> viewAllEmployees());
+        
+        clearButton = new JButton("Clear");
+        clearButton.addActionListener(e -> clearForm());
+        
+        buttonPanel.add(saveButton);
+        buttonPanel.add(viewButton);
+        buttonPanel.add(clearButton);
+        
+        gbc.gridx = 0;
+        gbc.gridy = 4;
+        gbc.gridwidth = 2;
+        gbc.weightx = 1.0;
+        panel.add(buttonPanel, gbc);
+        
+        return panel;
+    }
+    
+    private JPanel createTablePanel() {
+        JPanel panel = new JPanel(new BorderLayout());
+        panel.setBorder(BorderFactory.createTitledBorder("Employee Records"));
+        
+        // Create the table model with column names
+        String[] columnNames = {"Name", "Code", "Designation", "Salary"};
+        tableModel = new DefaultTableModel(columnNames, 0);
+        
+        // Create the table and add it to a scroll pane
+        employeeTable = new JTable(tableModel);
+        JScrollPane scrollPane = new JScrollPane(employeeTable);
+        
+        panel.add(scrollPane, BorderLayout.CENTER);
+        
+        return panel;
+    }
+    
+    private void initializeDatabase() {
+        try (Connection conn = getConnection()) {
+            // Create the employee table if it doesn't exist
+            String createTableSQL = 
+                "CREATE TABLE IF NOT EXISTS employees (" +
+                "id INT AUTO_INCREMENT PRIMARY KEY," +
+                "name VARCHAR(100) NOT NULL," +
+                "code VARCHAR(20) NOT NULL," +
+                "designation VARCHAR(100) NOT NULL," +
+                "salary DECIMAL(10, 2) NOT NULL)";
+            
+            try (Statement stmt = conn.createStatement()) {
+                stmt.execute(createTableSQL);
+                System.out.println("Database initialized successfully.");
+            }
+        } catch (SQLException e) {
+            showError("Database Initialization Error", e.getMessage());
+            e.printStackTrace();
+        }
+    }
+    
+    private void saveEmployee() {
+        // Get the input values
+        String name = nameField.getText().trim();
+        String code = codeField.getText().trim();
+        String designation = designationField.getText().trim();
+        String salaryStr = salaryField.getText().trim();
+        
+        // Validate the input
+        if (name.isEmpty() || code.isEmpty() || designation.isEmpty() || salaryStr.isEmpty()) {
+            showError("Input Error", "All fields are required.");
+            return;
+        }
+        
+        double salary;
+        try {
+            salary = Double.parseDouble(salaryStr);
+        } catch (NumberFormatException e) {
+            showError("Input Error", "Salary must be a valid number.");
+            return;
+        }
+        
+        // Insert the employee record into the database
+        try (Connection conn = getConnection()) {
+            String insertSQL = 
+                "INSERT INTO employees (name, code, designation, salary) " +
+                "VALUES (?, ?, ?, ?)";
+            
+            try (PreparedStatement pstmt = conn.prepareStatement(insertSQL)) {
+                pstmt.setString(1, name);
+                pstmt.setString(2, code);
+                pstmt.setString(3, designation);
+                pstmt.setDouble(4, salary);
+                
+                int rowsAffected = pstmt.executeUpdate();
+                if (rowsAffected > 0) {
+                    JOptionPane.showMessageDialog(this, 
+                        "Employee record saved successfully.", 
+                        "Success", JOptionPane.INFORMATION_MESSAGE);
+                    
+                    // Clear the form and refresh the table
+                    clearForm();
+                    viewAllEmployees();
+                }
+            }
+        } catch (SQLException e) {
+            showError("Database Error", e.getMessage());
+            e.printStackTrace();
+        }
+    }
+    
+    private void viewAllEmployees() {
+        // Clear the existing table data
+        tableModel.setRowCount(0);
+        
+        // Retrieve all employee records from the database
+        try (Connection conn = getConnection()) {
+            String selectSQL = "SELECT name, code, designation, salary FROM employees";
+            
+            try (Statement stmt = conn.createStatement();
+                 ResultSet rs = stmt.executeQuery(selectSQL)) {
+                
+                // Add each employee record to the table model
+                while (rs.next()) {
+                    String name = rs.getString("name");
+                    String code = rs.getString("code");
+                    String designation = rs.getString("designation");
+                    double salary = rs.getDouble("salary");
+                    
+                    Object[] row = {name, code, designation, salary};
+                    tableModel.addRow(row);
+                }
+                
+                if (tableModel.getRowCount() == 0) {
+                    JOptionPane.showMessageDialog(this, 
+                        "No employee records found.", 
+                        "Information", JOptionPane.INFORMATION_MESSAGE);
+                }
+            }
+        } catch (SQLException e) {
+            showError("Database Error", e.getMessage());
+            e.printStackTrace();
+        }
+    }
+    
+    private void clearForm() {
+        nameField.setText("");
+        codeField.setText("");
+        designationField.setText("");
+        salaryField.setText("");
+        nameField.requestFocus();
+    }
+    
+    private void showError(String title, String message) {
+        JOptionPane.showMessageDialog(this, message, title, JOptionPane.ERROR_MESSAGE);
+    }
+    
+    private Connection getConnection() throws SQLException {
+        return DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
+    }
+    
+    public static void main(String[] args) {
+        // Load the JDBC driver
+        try {
+            // For MySQL
+            Class.forName("com.mysql.cj.jdbc.Driver");
+            
+            // For PostgreSQL
+            // Class.forName("org.postgresql.Driver");
+            
+            // Create and display the GUI on the Event Dispatch Thread
+            SwingUtilities.invokeLater(() -> {
+                new EmployeeDatabase_Q26().setVisible(true);
+            });
+        } catch (ClassNotFoundException e) {
+            JOptionPane.showMessageDialog(null, 
+                "JDBC Driver not found. Please add the appropriate JDBC driver to the classpath.", 
+                "Driver Error", JOptionPane.ERROR_MESSAGE);
+            e.printStackTrace();
+        }
+    }
+}