for （int i = 0; i < 3; ++i）{}

This for loop is missing the third expression that specifies the increment/decrement of the loop variable. It should be:

for (int i = 0; i < 3; i++) {}

This loop will execute the code block inside the curly braces 3 times, with the loop variable i starting from 0 and incrementing by 1 each time until it reaches 2 (because the condition i < 3 will no longer be true when i is 3).