Is there a difference between multiple if statements and else if?

Question

If I write

int a = 1;
int b = 2;

if (a == b) {

//Do something

} else if (a > b) {

//Do something else

} else if (a < b) {

//Do something else

}

as opposed to:

if (a == b) {

//Do something

}
if (a > b) {

//Do something else

}
if (a < b) {

//Do something else

}

Is there a difference be it the way the compiler interprets the code or speed? I see no logical difference, but there surely must be a reason why an if else statement exists. It's just a single line break difference.

Answer 1

In the scenario above, they are the same, other than speed. If/else will be faster than a series of ifs, because else statements are skipped if the if condition is satisfied. In a series of ifs, on the other hand, each condition is evaluated separately.

In other scenarios, of course, the logic is not the same, and so replacing if/else with a series of ifs breaks the program. Example:

// this:
if(x <= 0) {
    x = 1;
}
else { // only true if x started out > 0
    x = 37;
}

// is different from this:
if(x <= 0) {
    x = 1;
}
if(x > 0) { // always true in this version
    x = 37;
}