Can you tell about your experience in improving resource efficiency in code on past projects?

In one of my Java projects, I optimized memory usage and CPU time through several approaches:

• Used lazy initialization of objects to create them only when necessary.
• Replaced heavy collections with lighter alternatives, such as ArrayList instead of LinkedList, when frequent insertion in the middle was not required.
• Applied thread and object pools for reuse, reducing the load on the garbage collector.
• Optimized algorithms by reducing the number of nested loops and avoiding redundant calculations.

Example of using an object pool:

// Example of a simple object pool for reuse
class ConnectionPool {
    private List<Connection> available = new ArrayList<>();

    public Connection getConnection() {
        if (available.isEmpty()) {
            return new Connection();
        } else {
            return available.remove(available.size() - 1);
        }
    }

    public void releaseConnection(Connection conn) {
        available.add(conn);
    }
}

These measures helped reduce resource consumption and improve application responsiveness.