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The do-while loop is an exit-controlled iteration statement that executes a block of code once before evaluating a boolean condition. Unlike the standard while loop, the do-while loop guarantees that the loop body runs at least one time, regardless of whether the condition is initially true or false.

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Syntax

do {
  // Statement(s) to be executed
} while (condition);

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Parameters

  • Statement(s): A block of code enclosed in braces {} that performs the loop’s operations.
  • Condition: An expression that evaluates to a bool. This is evaluated after the execution of the statement block.

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Execution Logic

  1. Body Execution: The program enters the do block and executes the statements contained within it.
  2. Condition Evaluation: Upon reaching the while keyword, the specified condition is evaluated.
  3. Branching:
    • If the condition evaluates to true, control returns to the beginning of the do block, and the process repeats.
    • If the condition evaluates to false, the loop terminates, and control passes to the next statement following the loop.

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Example

The following example demonstrates the syntax and execution flow. Note that the variable count is incremented inside the loop, eventually causing the condition count < 3 to evaluate to false. 
void main() {
  int count = 0;

  do {
    print('Current count: $count');
    count++;
  } while (count < 3);
}
Output: 
Current count: 0
Current count: 1
Current count: 2

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False Condition Behavior

Because the condition is evaluated at the end of the iteration, the body executes once even if the condition is false at the start. 
void main() {
  bool isReady = false;

  do {
    print('This executes exactly once.');
  } while (isReady);
}

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Loop Control Statements

The do-while loop supports standard Dart control flow statements:
  • break: Immediately terminates the loop, bypassing the condition check.
  • continue: Skips the remainder of the current iteration and jumps directly to the condition evaluation at the end of the loop.
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