集合框架

Arrays

Arrays - forEach

public inline fun <T> Array<out T>.forEach(action: (T) -> Unit): Unit {
    for (element in this) action(element)
}

Kotlin 集合

• Iterable
• MutableIterable
• Collection
• MutableCollection
• List
• MutableList
• Set
• MutableSet
• Map
• MutableMap

Collection

集合和函数操作符

总数操作符

过滤操作符

映射操作符

• map()

/**
 * Returns a list containing the results of applying the given [transform] function
 * to each element in the original collection.
 */
public inline fun <T, R> Iterable<T>.map(transform: (T) -> R): List<R> {
    return mapTo(ArrayList<R>(collectionSizeOrDefault(10)), transform)
}

/**
 * Applies the given [transform] function to each element of the original collection
 * and appends the results to the given [destination].
 */
public inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.mapTo(destination: C, transform: (T) -> R): C {
    for (item in this)
        destination.add(transform(item))
    return destination
}

• flatMap()

public inline fun <T, R> Iterable<T>.flatMap(transform: (T) -> Iterable<R>): List<R> {
    return flatMapTo(ArrayList<R>(), transform)
}

public inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.flatMapTo(destination: C, transform: (T) -> Iterable<R>): C {
    for (element in this) {
        val list = transform(element)
        destination.addAll(list)
    }
    return destination
}

元素操作符

产生操作符

顺序操作符