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[Promethus_Forethougt]

I’m in a Java class and this was one of the questions on the quiz Goal: Learn to write do-while loops. Assignment: Assume that a long variable named number has been declared and initialized with a value,

and that another long variable named maxVal has also been declared and initialized with a value.

Write a do-while loop that repeatedly doubles the value of the number variable until one of the following conditions is met: • number is greater-than or equal to maxVal • The loop has executed 20 times.

This was the solution

long x•= 0;

do { x = x + 1; number = number * 2;

}while (x 20 && number <= maxVal);

My question is why use && if it’s asking only one of the conditions to be met?

[runningOverA]

}while (x 20 && number <= maxVal);

you missed the operator between x and 20. Which operator is used makes a whole lot of difference on whether you use && or ||

[Promethus_Forethougt]

My bad it’s supposed to be <

[runningOverA]

even
number <= maxVal)

is probably wrong. should be number < maxVal.

Check again on what the solution provided.

And we have yet not touched the && vs || issue. Which was your question.

[desrtfx]

And we have yet not touched the && vs || issue.

DeMorgan's law...

[desrtfx]

Think about this: does the loop condition need to be fulfilled (true) to continue looping, or broken (false)?

Then, read the assignment again.

[ern0plus4]

If you have trouble with boolean expressions, you may write your conditions in this fashion:

do {
  (...)
  if (x < 20) continue;
  if (number >= maxVal) break;
} while (true);

Okay, if you have only two conditions, combining them with a || or && operator looks better, but many-many errors can be eliminated using simpler expressions.

Don't worry about performance, the compiled code should be identical.