Should conditions test for positive or negative results?

Question

Sorry if the title is rather ambiguous, I was not sure how to word it.

Is it better to phrase a condition such that the outcome you don't want enters the if statement then you exit the function or should I test for the outcome I do want and follow the statement with my code.

Maybe some examples would help:

What I mean by testing for negative result:

if(myObject == null) {
    return;
}

//do whatever with myObject

What I mean by testing for positive result:

if(myObject != null) {
    //do whatever with myObject
}

Sorry, if someone can word it better than me please do.

Answer 1

I personally prefer the first method of checking if the object is null then immediately returning. It allows the "real code" to stay unindented, linear, and can prevent many nested if statements, which I find to be more readable. Otherwise, both ways are valid and will have the same outcome. Choose whichever works best in your situation (which can depend on any else or else if statements).

Here's a good example:

if (object1 == null) {
    return;
}
// do some stuff
if (object2 == null) {
    return;
}
// do some stuff
if (object3 == null) {
    return;
}

Opposed to:

if (object1 != null) {
    // do some stuff
    if (object2 != null) {
        // do some stuff
        if (object3 != null) {
            // do some stuff
        }
    }
}

I find the first one to be much more readable.