You can use last, which returns the last element or throws a NoSuchElementException, if the list is empty. scala> List(1, 2, 3).last res0: Int = 3 If you do not know if the list is empty or not, you may consider using lastOption, which returns an Option. scala> List().lastOption res1: Option[Nothing] = None scala> List(1, … Read more
I think the easiest would be to write: var list = listOf(2,3) println(list) // [2, 3] list = listOf(1) + list println(list) // [1, 2, 3] There is no specific tail implementation, but you can call .drop(1) to get the same. You can make this head\tail more generic by writing these extension properties: val <T> … Read more
you can use last property for read/write, inherited-getter: last is a returns the last element from the given list. var lst = [“element1” , “element2” , “element3”]; lst.last // -> element3 or lst[lst.length-1] //-> element3
Future.sequence takes a List[Future[T]] and returns a Future[List[T]]. You can do Future.sequence(f) and then use map or onComplete on it to access the list of values.
That’s because num is a Char, i.e. the resulting values are the ascii value of that char. This will do the trick: val txt = “82389235” val numbers = txt.map { it.toString().toInt() } The map could be further simplified: map(Character::getNumericValue)
Iterations in Kotlin: Some Alternatives Like already said, forEachIndexed is a good way to iterate. Alternative 1 The extension function withIndex, defined for Iterable types, can be used in for-each: val ints = arrayListOf(1, 2, 3, 4, 5) for ((i, e) in ints.withIndex()) { println(“$i: $e”) } Alternative 2 The extension property indices is available … Read more
Default sort() is useful for Comparable object. If your class is not a Comparable, use: def orders = publicTrainingInstance.trainingOrder.sort { it.id } That code will sort by using passed id. See docs: http://groovy.codehaus.org/groovy-jdk/java/util/Collection.html#sort()
For the users who want the easiest way to access the id of a list : Use the “.json” hack ! add “.json” at the end of your board URL to display the same output of the API query for that board, in your browser ! (no other tool needed, no hassle dealing with authentication). … Read more
Just use .retainAll { … } or .removeAll { … }, both accepting a predicate, to filter it in-place: items.retainAll { shouldRetain(it) } items.removeAll { shouldRemove(it) } Note that items should be a MutableList<T> for that, not just List<T>, which is a read-only list in Kotlin and thus does not expose any mutating functions (see: … Read more
collect (defined on TraversableLike and available in all subclasses) works with a collection and a PartialFunction. It also just so happens that a bunch of case clauses defined inside braces are a partial function (See section 8.5 of the Scala Language Specification [warning – PDF]) As in exception handling: try { … do something risky … Read more