for loop VS while loop in programming languages, c++/java?

Question

Which is better for performance? This may not be consistent with other programming languages, so if they are different, or if you can answer my question with your knowledge in a

Answer 1

The example you posted actually has different behavior for while and for.

This:

for (int x = 0; x < 100; ++x) {
  foo y;
  y.bar(x);
}

Is equivalent to this:

{ // extra blocks needed
  int x = 0;
  while (x < 100) {
    {
      foo y;
      y.bar(x);
    }
    ++x;
  }
}

And you can expect the performance to be identical. Without the extra braces the meaning is different, and so the assembly generated may be different.

While the differences between the two is nonexistent on a modern compiler, for may optimize better as states its behavior more explicitly.