scala实现迭代器模式

package com.linewell.modeldesgin.iterator

import scala.collection.mutable.ArrayBuffer

/**
* 抽象迭代器特质
* Created by ctao on 2015/9/1.
*/
trait AbstractIterator {

/**
* 移至下一个元素
*/
def next(): Unit

/**
* 判断是否为最后一个元素
* @return 是否为最后一个元素
*/
def isLast: Boolean


/**
* 移至上一个元素
*/
def previous(): Unit


/**
* 判断是否为第一个元素
* @return 是否为第一个元素
*/
def isFirst: Boolean


/**
* 获取下一个元素
* @return 下一个元素
*/
def getNextItem: Any

/**
* 获取上一个元素
* @return 上一个元素
*/
def getPreviousItem: Any
}

/**
* 抽象聚合类
* @param objects 存放元素
*/
abstract class AbstractAnyArrayBuffer(objects: ArrayBuffer[Any]) {
def addAny(any: Any) = objects += any

def removeAny(any: Any) = objects -= any

def getAny = this.objects

def createIterator: AbstractIterator
}

/**
* 商品聚合类
* @param objects 存放元素
*/
class ProductArrayBuffer(objects: ArrayBuffer[Any]) extends AbstractAnyArrayBuffer(objects) {
override def createIterator = new ProductIterator

/**
* 内部类实现
*/
protected class ProductIterator extends AbstractIterator {
/**
* 正向遍历游标
*/
private var cursor1: Int = 0

/**
* 反向遍历游标
*/
private var cursor2: Int = objects.length - 1


override def next(): Unit = {
if (cursor1 < objects.length) {
cursor1 += 1
}
}

override def isLast: Boolean = cursor1 == objects.length


override def previous(): Unit = {
if (cursor2 > -1) {
cursor2 -= 1
}
}


override def isFirst: Boolean = cursor2 == -1

override def getNextItem = objects(cursor1)


override def getPreviousItem = objects(cursor2)


}

}

/**
* 不采用内部类
* @param objects 存放元素
*/
class ProductArrayBuffer2(objects: ArrayBuffer[Any]) extends AbstractAnyArrayBuffer(objects) {
override def createIterator = new ProductIterator2(this)
}

/**
* 不采用内部类
* @param productArrayBuffer2 商品聚合类
*/
class ProductIterator2(productArrayBuffer2: ProductArrayBuffer2) extends AbstractIterator {
private val products = productArrayBuffer2.getAny
private var cursor1: Int = 0
private var cursor2: Int = products.length - 1


override def next(): Unit = {
if (cursor1 < products.length) {
cursor1 += 1
}
}

override def isLast: Boolean = cursor1 == products.length


override def previous(): Unit = {
if (cursor2 > -1) {
cursor2 -= 1
}
}


override def isFirst: Boolean = cursor2 == -1

override def getNextItem = products(cursor1)


override def getPreviousItem = products(cursor2)


}

package com.linewell.modeldesgin.iterator

import scala.collection.mutable.ArrayBuffer

/**
* 测试客户端
* 迭代器模式，其实scala对反向遍历的支持比java好很多，我们完全可以使用自身的去实现反向遍历
* 即将迭代器直接reverse即可
* 但此次通过自定义游标的方式结合内部类和外部类两种方式实现
* Created by ctao on 2015/9/1.
*/
object Client extends App {
var products = new ArrayBuffer[Any]()

products += "a"
products += "b"
products += "c"
products += "d"
products += "e"

println("正向遍历")
products.foreach(x =>print(x+", "))
println()
println("-------------------------")
println("反向遍历")
products.reverse.foreach(x =>print(x+", "))
println()

val arrayBuffer1: AbstractAnyArrayBuffer = new ProductArrayBuffer(products)

arrayBuffer1.removeAny("a")
arrayBuffer1.addAny("cc")

val iterator1: AbstractIterator = arrayBuffer1.createIterator

println("正向遍历")


while (!iterator1.isLast) {
print(iterator1.getNextItem + ", ")
iterator1.next()
}

println()
println("---------------------------")
println("逆向遍历")
while (!iterator1.isFirst) {
print(iterator1.getPreviousItem + ", ")
iterator1.previous()
}

println()


val arrayBuffer2: AbstractAnyArrayBuffer = new ProductArrayBuffer2(products)

arrayBuffer2.removeAny("b")
arrayBuffer2.addAny("cca")

val iterator2: AbstractIterator = arrayBuffer2.createIterator

println("正向遍历")


while (!iterator2.isLast) {
print(iterator2.getNextItem + ", ")
iterator2.next()
}

println()
println("---------------------------")
println("逆向遍历")
while (!iterator2.isFirst) {
print(iterator2.getPreviousItem + ", ")
iterator2.previous()
}

}