Clean code chapter 3(Robert C.martin)

 

Summary: -------- 

1. Functions should hardly ever be 20 lines long.

 2.Keep blocks (inside if, else, while, for, etc.) short.

 Ideally, just one line long. And that line should usually be a function call with a descriptive name. Don’t let functions get so big that they require deep nesting.

 If you see more than 1–2 levels of indentation, it’s a smell.

 Break the nested logic into smaller functions.

 Example: Problem: Deep nesting(messy)

 public void handleOrder(Order order) {
    if (order != null) {
        if (order.hasItems()) {
            for (Item item : order.getItems()) {
                if (item.isInStock()) {
                    // process item
                    System.out.println("Processing item: " +                                 item.getName());
                    item.setStatus("PROCESSED");
                } else {
                    System.out.println("Item out of stock: " +                             item.getName());
                }
            }
        } else {
            System.out.println("Order has no items.");
        }
    } else {
        System.out.println("Order is null.");
    }
}

Clean Code:

 public void handleOrder(Order order) {
    if (isProcessable(order)) {
        processOrder(order);
    }
}

// ---- helper functions ----

private boolean isProcessable(Order order) {
    return order != null && order.hasItems();
}

private void processOrder(Order order) {
    for (Item item : order.getItems()) {
        processItem(item);
    }
}

private void processItem(Item item) {
    if (item.isInStock()) {
        markItemAsProcessed(item);
    } else {
        logOutOfStock(item);
    }
}

private void markItemAsProcessed(Item item) {
    System.out.println("Processing item: " + item.getName());
    item.setStatus("PROCESSED");
}

private void logOutOfStock(Item item) {
    System.out.println("Item out of stock: " + item.getName());
}

3. Do one thing:   

If you can extract a piece of code into a well-named function that adds understanding, your original function is probably doing more than one thing.