Which loop construct guarantees the loop body executes at least once?

• A. For loop
• B. While loop
• C. For-each loop
• D. Do-While loop

Answer: (D)

The concept being tested is when the loop condition is checked relative to the loop body and how that affects whether the body runs at least once.

A do-while loop runs the loop body first and then checks the condition. Because the body is executed before any condition is tested, the code inside the loop executes at least once, even if the condition is false on the first check.

In contrast, a for loop and a while loop evaluate their condition before running the body. If the condition is false at the start, the body may not run at all. A for-each loop iterates over elements of a collection, so if the collection is empty, the body won’t run either. Therefore, the do-while loop uniquely guarantees at least one execution of its body.