#18 Do while Loop In JAVA | Skyhighes | Lecture 18

Do-While Loops in Java: The "At Least Once" Guarantee

Imagine you have a task that needs to be done at least once, even if the condition for repetition isn't initially met. That's where the do-while loop steps in, a close cousin of the while loop with a unique twist.

Here's how it works:

Action First, Questions Later: The code block within the loop executes before the condition is checked for the first time.
Condition Check: After the initial execution, the condition is evaluated.
Loop or Exit: If the condition is true, the loop body executes again. This cycle continues until the condition becomes false.
Guaranteed Execution: This ensures that the code block runs at least once, even if the condition is initially false.
Syntax:

Java
do {
// Code to be executed at least once
} while (condition);
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Example:

Java
int choice = 0;
do {
System.out.println("Enter a number (1-5): ");
choice = input.nextInt(); // Assume input is a Scanner object
} while (choice < 1 || choice > 5); // Keep asking until a valid choice is made
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Key Points:

Guaranteed Execution: The code block always runs at least once, making it ideal for tasks that require initialization or input before checking conditions.

Condition Check: The condition is still crucial, as it determines whether the loop continues after the initial execution.

Syntax Difference: The do keyword comes before the code block, and the while statement with the condition comes after.

Common Use Cases:

Prompting for user input until a valid value is entered
Implementing menus that should always display at least once
Reading data from a file until the end is reached (ensuring at least one read attempt)
Handling game logic that requires an initial action before checking game state
Remember: Do-while loops offer flexibility by ensuring a minimum execution. However, use them judiciously to avoid unintended consequences. When in doubt, the standard while loop is often a safer choice for general repetition tasks.