Understanding DART syntax: Identifiers, Datatypes, variables, comments; Decision making (if, if..else, if..else if..., switch..case); Iterative statements (for, for...in loop, while, do..while); break, continue, label

📖 Theory

Read it cold

Before any teaching, read this Dart and predict its output:

int day = 2;

if (day == 2) {

print('Workshops today');

} else {

print('Regular schedule');

}

You read it perfectly: it prints Workshops today: because Dart's control flow IS your Java, in a lighter jacket. This lesson tours the whole syntax the fast way: skate over the familiar, brake hard at the 4 places Dart differs.

📊 At a glance

Datatypes (brake at rows 3, 6 and 7)

📖 Theory

Variables and comments: the accents

var deduces the type from the initializer and fixes it: var seats = 350; makes seats an int; seats = 'full'; later is a compile error. Inference is not looseness.

dynamic is the true opt-out (checking deferred to runtime): rare, deliberate.

final = set once, at runtime (final festName = fetchName();); const = a compile-time constant (const maxSeats = 350;).

Comments: // and /* */ as in Java, plus /// documentation comments that tooling reads: Flutter's libraries are annotated this way.

⌨️ Practical

Decisions, every loop, and the label trick

void main() {
  var events = ['Garba Night', 'Coding Contest', 'Robo Race'];
  int day = 2;

  // switch: Java-shaped, break per non-empty case
  switch (day) {
    case 1:
      print('Inaugration day');
      break;
    case 2:
      print('Workshops today');
      break;
    default:
      print('Regular schedule');
  }

  // for-in: the collection walker (new accent)
  for (var e in events) {
    print(e);
  }

  // classic for, while, do-while: exactly your Java
  for (int i = 0; i < 2; i++) { print('pass $i'); }

  // LABEL: break out of BOTH loops in one jump
  outer:
  for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
      if (i * j == 4) {
        print('found at i=$i, j=$j');   // i=2, j=2
        break outer;                    // exits both loops
      }
    }
  }
}

🧩 Quiz

var seats = 350; and 2 lines later: seats = 'Housefull'; What does Dart say?

1. Fine: var means the type can change anytime
2. Compile error: var inferred int at initialization and the type is fixed forever
3. Runtime error when the String is first used as a number
4. Fine, but seats becomes dynamic from then on

💭 Think first

Trace the label

In the listing's nested loop, walk i and j by hand: which (i, j) pairs run before the break, what prints, and what would plain break (no label) have done differently?

⚠️ Watch out

The 4 accents that catch Java speakers

var is fixed-typed: the quiz; write it on your wrist.

String has a capital S: string does not compile; and single quotes are the house idiom.

List, not arrays: no int[] syntax; events[0] works, .length is a property (no brackets: Java's array .length, not String's .length()).

No standalone char: 'G' is just a 1-character String.

📖 Theory

Skate and brake: the second-language method

You just learned 90% of a language in one lesson because you invested in Java properly: that is transfer, and it is the real syllabus. Keep the accent list where you revise, and practise ONLY the accents: the familiar parts maintain themselves. One language piece remains before Flutter: functions, where Dart hides its best new tricks (arrow bodies, named parameters), next.

✅ Summary

Key takeaways

• Identifiers and comments: Java's rules, plus /// documentation comments.
• Types: int, double, num (either), String (capital S), bool, List (the growable array), Map.
• var infers ONCE from the initializer and fixes the type; dynamic is the rare opt-out; final runtime-once, const compile-time.
• if/else if/else and switch-case: Java-shaped, break per non-empty case.
• Loops: for, for-in for collections, while, do-while; break and continue as known.
• A label (outer:) lets break outer; escape nested loops in one jump: traced at i=2, j=2.
• Memory hook: skate the familiar, brake at var, String, List, for-in.