String Concatenation and Formatting

String name = 'Thabo';
Integer orderNumber = 4821;
String message = 'Hi ' + name + ', your order #' + orderNumber + ' is confirmed.';

1. String name = 'Thabo'; — the customer's name.
2. Integer orderNumber = 4821; — the order number, as a real number this time.
3. String message = ... — builds the sentence with +, the same concatenation from Module 3.

This works, but gets harder to read as more variables join in — every + is a small interruption to the sentence you're building.

String.format() needs its placeholder values grouped together as a single list, written like this:

new List<String>{ name, String.valueOf(orderNumber) }

1. new List<String>{ name, String.valueOf(orderNumber) } — breaking this one line into its three parts:
   • new creates the list itself — you'll see new again for creating other kinds of values later in this course; here, it's simply "make a new list."
   • List<String> means "a list that holds String values."
   • { name, String.valueOf(orderNumber) } is the list's actual contents, comma-separated, in order.

That's the entire shape you need for now — a full, dedicated lesson on lists (adding items, reading them back, looping over them) comes in Module 7. Here, just recognize new List<String>{ ... } as "the values String.format() slots into the message," in the exact order they appear.

String message = String.format(
    'Hi {0}, your order #{1} is confirmed.',
    new List<String>{ name, String.valueOf(orderNumber) }
);

1. String message = String.format( — calls String.format(), opening its argument list, which spans the next two lines.
2. 'Hi {0}, your order #{1} is confirmed.', — the message template. {0} and {1} are placeholders.
3. new List<String>{ name, String.valueOf(orderNumber) } — the values that fill those placeholders, in order: {0} becomes name, {1} becomes the converted orderNumber.
4. ); — closes the call.

Note that String.format() expects String values in that list — non-string values (like our Integer) need converting first, using exactly the String.valueOf() you met last lesson.

An order-confirmation message with several dynamic parts — customer name, order number, delivery date — is a natural fit for String.format(): the sentence structure stays visible and readable, instead of getting broken up by + operators every few words.

For a simple, one- or two-variable message, plain + concatenation is often just as readable and involves less ceremony (no building a List). String.format() earns its keep once you have three or more variables, or when the same message template gets reused in multiple places.