Stack.kt

/**
 * Created by gazollajunior on 03/04/16.
 */


class Stack<T:Comparable<T>>(list:MutableList<T>):Iterator<T> {

    var itCounter: Int = 0

    var items: MutableList<T> = list


    fun isEmpty():Boolean = this.items.isEmpty()

    fun count():Int = this.items.count()

    fun push(element:T) {
        val position = this.count()
        this.items.add(position, element)
    }

    override  fun toString() = this.items.toString()

    fun pop():T? {
        if (this.isEmpty()) {
            return null
        } else {
            val item =  this.items.count() - 1
            return this.items.removeAt(item)
        }
    }

    fun peek():T? {
        if (isEmpty()) {
            return null
        } else {
            return this.items[this.items.count() - 1]
        }
    }

// Note Let the default implementation exist

//    override fun toString(): String {
//        val topDivider = "---Stack---\n"
//        val bottomDivider = "\n-----------"
//
//        val stackElements = array.map {
//            "$it"
//        }.reversed().joinToString("\n")
//
//        return topDivider + stackElements + bottomDivider
//
//    }

    override fun hasNext(): Boolean {
        val hasNext = itCounter < count()

        // As soon as condition fails, reset the counter
        if (!hasNext) itCounter = 0

        return hasNext
    }

    override fun next(): T {
        if (hasNext()) {
            val topPos: Int = (count() - 1) - itCounter
            itCounter++
            return this.items[topPos]
        } else {
            throw NoSuchElementException("No such element")
        }
    }

}

fun main(args: Array<String>) {

    var initialValue =  mutableListOf<Int>(10)
    var stack = Stack<Int>(initialValue)
    println(stack)
    stack.push(22)
    println(stack)
    stack.push(55)
    println(stack)
    stack.push(77)
    println(stack)
    stack.pop()
    println(stack)

    for (item in stack) println("Item in stack : " + item)

}