scala的多种集合的使用(8)之队列和栈的操作方法

1.使用队列

队列是一种那个先进先出的队列。
1)创建一个队列。

scala> import scala.collection.mutable.Queue
import scala.collection.mutable.Queue

scala> var fruits = Queue[String]()
fruits: scala.collection.mutable.Queue[String] = Queue()

scala> fruits += "apple"
res66: scala.collection.mutable.Queue[String] = Queue(apple)

scala> fruits += ("orange","banana")
res67: scala.collection.mutable.Queue[String] = Queue(apple, orange, banana)

scala> fruits ++= List("cherry","cocount")
res68: scala.collection.mutable.Queue[String] = Queue(apple, orange, banana, cherry, cocount)

scala> fruits.enqueue("pine")

scala> fruits
res70: scala.collection.mutable.Queue[String] = Queue(apple, orange, banana, cherry, cocount, pine)

2)dequeue每次从队列头部删除一个元素。

scala> val next = fruits.dequeue
next: String = apple

scala> fruits
res72: scala.collection.mutable.Queue[String] = Queue(orange, banana, cherry, cocount, pine)

3)dequeueFirst和dequeueAll方法可以从队列中删除多个元素。

scala> var fruits = Queue[String]()
fruits: scala.collection.mutable.Queue[String] = Queue()

scala> fruits ++= List("cherry","cocount")
res76: scala.collection.mutable.Queue[String] = Queue(cherry, cocount)

scala> fruits ++= List("orange","apple")
res77: scala.collection.mutable.Queue[String] = Queue(cherry, cocount, orange, apple)

scala> fruits.dequeueFirst(_.startsWith("a"))
res79: Option[String] = Some(apple)

scala> fruits
res80: scala.collection.mutable.Queue[String] = Queue(cherry, cocount, orange)

scala> fruits.dequeueAll(_.length > 6)
res81: scala.collection.mutable.Seq[String] = ArrayBuffer(cocount)

scala> fruits
res82: scala.collection.mutable.Queue[String] = Queue(cherry, orange)

2.使用栈

栈是一种后进先出的数据结构。用push方法将元素入栈，用pop方法将元素出栈。
1)创建一个任意数据类型空的可变栈。

scala> import scala.collection.mutable.Stack
import scala.collection.mutable.Stack

scala> var ints = Stack[Int]()
ints: scala.collection.mutable.Stack[Int] = Stack()

2)在创建时给栈初始元素。

scala> val ints = Stack(1,2,3)
ints: scala.collection.mutable.Stack[Int] = Stack(1, 2, 3)

3)用push方法向栈中填充元素。

scala> var fruits = Stack[String]()
fruits: scala.collection.mutable.Stack[String] = Stack()

scala> fruits.push("apple")
res2: scala.collection.mutable.Stack[String] = Stack(apple)

scala> fruits.push("apple","orange","banana")
res3: scala.collection.mutable.Stack[String] = Stack(banana, orange, apple, appl

4)用pop方法将元素出栈。

scala> val next = fruits.pop
next: String = banana

scala> fruits
res4: scala.collection.mutable.Stack[String] = Stack(orange, apple, apple)

5)用top方法查看下一个元素。

scala> fruits.top
res5: String = orange

scala> fruits
res6: scala.collection.mutable.Stack[String] = Stack(orange, apple, apple)

6)用clear清空一个可变栈。

scala> fruits.clear

scala> fruits
res8: scala.collection.mutable.Stack[String] = Stack()