how to use distinct operator

Question

would you please let me know the reason why I am getting the output mentioned below?? I expected to get the following out put:

[Person(_name=xyz4, _age=30),   
Person(_name=xyz5, _age=50)]

because of distinct operator

Main:

fun main(args: Array<String>) {
val person1 = Person("xyz1", 10);
val person2 = Person("xyz2", 20);
val person3 = Person("xyz3", 30);
val person4 = Person("xyz4", 30);
val person5 = Person("xyz5", 50);

var persons = listOf(
person1, person2, person3, person4 , person5)
.asSequence()
.filter { x-> x.age >=30 }
.distinct()

println(persons.toList())
}

output:

[Person(_name=xyz3, _age=30), Person(_name=xyz4, _age=30), 
Person(_name=xyz5, _age=50)]

`distinct` removes duplicates, but there are no duplicates. Why do you think it should remove `Person(_name=xyz3, _age=60)`? — marstran, Sep 28 '18 at 13:48
Note that the output doesn't match the input. there is no person with name xyz3 and age 60 in your input. So you're probably not getting the output you posted, or you probably didn't use the inpt you posted. — JB Nizet, Sep 28 '18 at 13:56
@LetsamrIt Where does `Person(_name=xyz4, _age=30)` come from? That person doesn't exist in your input list. — marstran, Sep 28 '18 at 14:27
Voting to close since, despite our requests, you're not posting the actual code and/or output. — JB Nizet, Sep 28 '18 at 14:28

score 1 · Answer 1 · 2018-09-28T15:03:03.207

you can use

.distinctBy { it.age }

instead of

.distinct()

if order of elements is important you can add sortedBy like this

fun main(args: Array<String>) {
    val person1 = Person("xyz1", 10)
    val person2 = Person("xyz2", 20)
    val person3 = Person("xyz3", 30)
    val person4 = Person("xyz4", 30)
    val person5 = Person("xyz5", 50)

    val persons = listOf(
            person1, person2, person3, person4, person5)
            .reversed()
            .filter { x -> x.age >= 30 }
            .distinctBy { it.age }
            .sortedBy { it.age }

    println(persons.toList())
}

how to use distinct operator

1 Answers1