CODEWITHSUNDEEP
androidstringnull
Nxtpr
Nxtpr

Reputation: 21

Object null in Android

I got strange results with null and strings:

"" + null result is null, 
null + "" result is null
"bbb" + null result is "bbbnull"

I expected "", "" and "bbb"

Where did I go wrong?

Upvotes: 0

Views: 80

Answers (1)

Dương Minh
Dương Minh

Reputation: 2421

When you attach a string as null + "", it means that the compiler will interpret it null.toString() and "".

And for null.toString(), check out Kotlin's toString() extension.

fun Any?.toString(): String {
    if (this == null) return "null"
    // after the null check, 'this' is autocast to a non-null type, so the toString() below
    // resolves to the member function of the Any class
    return toString()
}

As you can see, when you pass in null, it will print "null". That's why you get "null" instead of not seeing it.

Upvotes: 2

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