Find Item In Kotlin Arrays Return Null

Question

I'm having this class

class Product(val price: BigDecimal, val tag: String)

Then I add items to this class

 var products = ArrayList<Product>()

 for (i in 1..5) {
     products.add(Product((0.25 * i).toBigDecimal(), i.toString()))
 }

Now I can view the items like this

products.forEach {
    Log.d("xxx", "price: ${it.price} tag: ${it.tag}")
}

Results:

D/xxx: price: 0.25 tag: 1
D/xxx: price: 0.5 tag: 2
D/xxx: price: 0.75 tag: 3
D/xxx: price: 1.0 tag: 4
D/xxx: price: 1.25 tag: 5

What I'm trying to do is, find "price" with "tag" = "3" in products. I'm using this code but it gives me null.

var f = products.find { it.tag.equals('3') }

Any ideas?

Keyur Nimavat · Accepted Answer · 2020-09-20 04:24:45Z

1

Answer is already inside your question.

You are trying to save tag as "tag" = "3" but you are trying to retrieve with it.tag.equals('3').

Simply you have to change your code with it.tag.equals("3")

Replace this line

var f = products.find { it.tag.equals('3') }

with this

 var f = products.find { it.tag.equals("3") }

answered Sep 20, 2020 at 4:24

Keyur Nimavat

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Comments

aminography · Accepted Answer · 2020-09-20 04:32:12Z

1

The problem is that "3" and '3' are different. '3' is the character of the number 3 and "3" is a string that contains the character of 3. By using equals function, in fact, you are getting false always in the predicate due to inequality of String and Char types. So, if you change the code like the following, the problem will be solved:

var f = products.find { it.tag == "3" }

Note that == in kotlin is the operator function of equals which makes it simpler to read and write.

edited Sep 20, 2020 at 4:32

answered Sep 20, 2020 at 4:20

aminography

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