Here are some examples of how to perform common SQL operations (insert, select, update, and delete) using JDBC in Java:

1. Insert a record into a table

// 1. Load the JDBC driver
Class.forName("com.mysql.cj.jdbc.Driver");

// 2. Create a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/mydatabase", "username", "password");

// 3. Create a statement and execute the SQL insert statement
Statement stmt = conn.createStatement();
String sql = "INSERT INTO employees (name, salary) VALUES ('John Doe', 50000.0)";
int rows = stmt.executeUpdate(sql);
System.out.println("Inserted " + rows + " row(s)");

// 4. Clean up resources
stmt.close();
conn.close();

2. Select records from a table

// 1. Load the JDBC driver
Class.forName("com.mysql.cj.jdbc.Driver");

// 2. Create a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/mydatabase", "username", "password");

// 3. Create a statement and execute the SQL select statement
Statement stmt = conn.createStatement();
String sql = "SELECT * FROM employees WHERE salary > 50000.0";
ResultSet rs = stmt.executeQuery(sql);

// 4. Process the result set
while (rs.next()) {
    String name = rs.getString("name");
    double salary = rs.getDouble("salary");
    System.out.println(name + " earns $" + salary);
}

// 5. Clean up resources
rs.close();
stmt.close();
conn.close();

3. Update a record in a table

// 1. Load the JDBC driver
Class.forName("com.mysql.cj.jdbc.Driver");

// 2. Create a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/mydatabase", "username", "password");

// 3. Create a statement and execute the SQL update statement
Statement stmt = conn.createStatement();
String sql = "UPDATE employees SET salary = 55000.0 WHERE name = 'John Doe'";
int rows = stmt.executeUpdate(sql);
System.out.println("Updated " + rows + " row(s)");

// 4. Clean up resources
stmt.close();
conn.close();

4. Delete a record from a table

// 1. Load the JDBC driver
Class.forName("com.mysql.cj.jdbc.Driver");

// 2. Create a connection to the database
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/mydatabase", "username", "password");

// 3. Create a statement and execute the SQL delete statement
Statement stmt = conn.createStatement();
String sql = "DELETE FROM employees WHERE name = 'John Doe'";
int rows = stmt.executeUpdate(sql);
System.out.println("Deleted " + rows + " row(s)");

// 4. Clean up resources
stmt.close();
conn.close();

Note that you may need to modify the connection URL and login credentials to match your database configuration. Also, be aware that using string concatenation to build SQL statements can be vulnerable to SQL injection attacks, so it's generally recommended to use prepared statements instead.