SagarKisanAvhad/Kotlin-important-functions-on-Collections-

Kotlin-important-functions-on-Collections-

1. How to create Map from array or list or set [associate()]

    val array: Array<String> = arrayOf("Android", "Kotlin", "IOS","Swift")
    val list = array.asList()
    val set = array.toSet()
    
    val mapFromArray = array.associateBy {
        it
    }
   
    val mapFromList = list.associate {
        Pair(it, it.length)
    }
   
    val mapFromSet = set.associate {
        Pair(it, it.length)
    }
   

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2. How to get index of last element in array or list [lastIndex]

In Java, we get last index array.length -1 in case Array and list.size() - 1 in case of List but in Kotlin we get lastIndex property with array and list.

    val array: Array<String> = arrayOf("Android", "Kotlin", "IOS","Swift")
    val lastIndexInArray = array.lastIndex
    
    val list = array.asList()
    val lastIndexInList = list.lastIndex

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3. How to check wheather all elements in Collection are satisfying condition . [all()]

this function return true when all elements in collection fullfilling mentioned condition

    val personAgeList = listOf<Int>(23,21,27,30,36,19)
    val isAllPersonAboveEighteen = personAgeList.all {age ->
        age > 18
    }

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4. How to check wheather any element in Collection is following condition. [any()] this function check, if that collection contains any element that fullfill mentioned condition

   val personList = listOf<Int>(25,21,28,13,6,29)
   val isAnyTeenager = personList.any{age ->
       age in 13..19
   }
   

note: this function is different from any() function that tells Collection contains any element or not.

5. chunked function

    val personList = listOf<Int>(25,21,28,13,6,29,33,34,56,45)
    val list = personList.chunked(5) //list will have two elements. first element will be list of first 5 elements in personList. Second element will be list of next 5 elements.
   

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