impl ch08 and browser demo

scala/src/main/scala/ch07_linkedlist/LinkedListAlgo.scala

@@ -2,8 +2,6 @@ package ch07_linkedlist
 
 import ch06_linkedlist.Node
 
-import scala.util.control.Breaks._
-
 object LinkedListAlgo {
 
   //reverse a linked list

scala/src/main/scala/ch08_stack/BrowserDemo.scala

@@ -0,0 +1,31 @@
+package ch08_stack
+
+class BrowserDemo(var currentPageOpt: Option[String], val backStack: StackDemo[String],
+                  val forwardStack: StackDemo[String]) {
+
+  def this() = this(None, new StackDemo[String], new StackDemo[String])
+
+  def open(page: String) = {
+    currentPageOpt.foreach(backStack.push)
+    forwardStack.clear()
+    currentPageOpt = Some(page)
+  }
+
+  def canGoBack(): Boolean = backStack.size > 0
+
+  def goBack(): Unit = {
+    backStack.pop().foreach(page => {
+      forwardStack.push(currentPageOpt.get)
+      currentPageOpt = Some(page.data)
+    })
+  }
+
+  def canGoForward(): Boolean = forwardStack.size > 0
+
+  def goForward(): Unit = {
+    forwardStack.pop().foreach(page => {
+      backStack.push(currentPageOpt.get)
+      currentPageOpt = Some(page.data)
+    })
+  }
+}

scala/src/main/scala/ch08_stack/StackDemo.scala

@@ -0,0 +1,32 @@
+package ch08_stack
+
+class Node[T](var data: T, var next: Option[Node[T]])
+
+class StackDemo[T] {
+
+
+  var headOpt: Option[Node[T]] = None
+  var size = 0
+
+  def clear(): Unit = {
+    headOpt = None
+    size = 0
+  }
+
+  def push(data: T) = {
+    val newHead = new Node(data, headOpt)
+    headOpt = Some(newHead)
+    size += 1
+  }
+
+  def pop(): Option[Node[T]] = {
+    headOpt match {
+      case None => None
+      case Some(head) =>
+        headOpt = head.next
+        size -= 1
+        Some(head)
+
+    }
+  }
+}

scala/src/test/scala/ch08_stack/BrowserDemoTest.scala

@@ -0,0 +1,74 @@
+package ch08_stack
+
+import org.scalatest.{FlatSpec, Matchers}
+
+class BrowserDemoTest extends FlatSpec with Matchers {
+
+  behavior of "BrowserDemoTest"
+
+  it should "canGoBack" in {
+    val browser = new BrowserDemo()
+    assert(!browser.canGoBack())
+    browser.open("a")
+    assert(!browser.canGoBack())
+    browser.open("b")
+    assert(browser.canGoBack())
+    browser.currentPageOpt.get should equal("b")
+  }
+
+  it should "goBack" in {
+    val browser = new BrowserDemo()
+    browser.open("a")
+    browser.open("b")
+    browser.currentPageOpt.get should equal("b")
+    assert(browser.canGoBack())
+    browser.goBack()
+    assert(!browser.canGoBack())
+    browser.currentPageOpt.get should equal("a")
+  }
+
+  it should "canGoForward" in {
+    val browser = new BrowserDemo()
+    browser.open("a")
+    browser.open("b")
+    browser.currentPageOpt.get should equal("b")
+    assert(browser.canGoBack())
+    browser.goBack()
+    assert(!browser.canGoBack())
+    browser.currentPageOpt.get should equal("a")
+    assert(browser.canGoForward())
+  }
+
+  it should "goForward" in {
+    val browser = new BrowserDemo()
+    browser.open("a")
+    browser.open("b")
+    browser.currentPageOpt.get should equal("b")
+    assert(browser.canGoBack())
+    browser.goBack()
+    assert(!browser.canGoBack())
+    browser.currentPageOpt.get should equal("a")
+    assert(browser.canGoForward())
+    browser.goForward()
+    browser.currentPageOpt.get should equal("b")
+  }
+
+  it should "open new page to clear forward stack" in {
+    val browser = new BrowserDemo()
+    browser.open("a")
+    browser.open("b")
+    browser.currentPageOpt.get should equal("b")
+    assert(browser.canGoBack())
+    browser.goBack()
+    assert(!browser.canGoBack())
+    browser.currentPageOpt.get should equal("a")
+    assert(browser.canGoForward())
+    browser.open("c")
+    assert(!browser.canGoForward())
+    browser.goBack()
+    browser.currentPageOpt.get should equal("a")
+  }
+
+
+
+}

scala/src/test/scala/ch08_stack/StackDemoTest.scala

@@ -0,0 +1,29 @@
+package ch08_stack
+
+import org.scalatest.{FlatSpec, Matchers}
+
+class StackDemoTest extends FlatSpec with Matchers {
+
+  behavior of "StackDemoTest"
+
+  it should "push/pop should be FILO" in {
+    val stack = new StackDemo[String]
+    val num = 100
+    for (i <- 1 to num) {
+      stack.push(i.toString)
+    }
+
+    for (i <- num to 1 by -1) {
+      stack.pop().get.data should equal(i.toString)
+    }
+  }
+
+  it should "pop should also work for empty stack" in {
+    val stack = new StackDemo[Int]
+    val num = 100
+    for (i <- num to 1 by -1) {
+      assert(stack.pop().isEmpty)
+    }
+  }
+
+}