diff --git a/src/main/scala/practise8/comprehensive/Comprehensive.scala b/src/main/scala/practise8/comprehensive/Comprehensive.scala
new file mode 100644
index 0000000..3abbc36
--- /dev/null
+++ b/src/main/scala/practise8/comprehensive/Comprehensive.scala
@@ -0,0 +1,45 @@
+package practise8.comprehensive
+/*
+* 练习 6 ⭐⭐ 综合题
+
+给：
+val sentences = List(
+  "hello scala",
+  "hello spark",
+  "scala is fun"
+)
+
+使用 flatMap 得到所有单词：
+List(
+  hello,
+  scala,
+  hello,
+  spark,
+  scala,
+  is,
+  fun
+)
+
+然后继续使用 filter：
+只保留长度 >= 5 的单词
+
+最终：
+List(hello, scala, hello, spark, scala)
+
+要求尝试写成：
+val result = sentences
+  .flatMap(...)
+  .filter(...)*/
+
+object Comprehensive {
+  def main(args: Array[String]): Unit = {
+    val sentences = List(
+      "hello scala",
+      "hello spark",
+      "scala is fun"
+    )
+    val result = sentences.flatMap(_.split(" "))
+      .filter(_.length >= 5)
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/demo/Demo1NestedCollection.scala b/src/main/scala/practise8/demo/Demo1NestedCollection.scala
new file mode 100644
index 0000000..9a04d86
--- /dev/null
+++ b/src/main/scala/practise8/demo/Demo1NestedCollection.scala
@@ -0,0 +1,20 @@
+package practise8.demo
+
+/*
+* 第 8 课：flatMap 和嵌套集合。
+* */
+object Demo1NestedCollection {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3) // 普通集合
+
+    // 嵌套集合
+    val nums2 = List(
+      List(1, 2),
+      List(3, 4),
+      List(5, 6)
+    )
+    println(nums2)
+
+
+  }
+}
diff --git a/src/main/scala/practise8/demo/Demo2MapNested.scala b/src/main/scala/practise8/demo/Demo2MapNested.scala
new file mode 100644
index 0000000..f656711
--- /dev/null
+++ b/src/main/scala/practise8/demo/Demo2MapNested.scala
@@ -0,0 +1,14 @@
+package practise8.demo
+
+/*
+* map 产生嵌套集合*/
+object Demo2MapNested {
+  def main(args: Array[String]): Unit = {
+    // map 遇到嵌套集合会怎样？
+    val nums = List(1, 2, 3)
+
+    val result = nums.map(x => List(x, x * 10)) // 每次返回的不是一个数字，而是一个 List。
+
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/demo/Demo3FlatMap.scala b/src/main/scala/practise8/demo/Demo3FlatMap.scala
new file mode 100644
index 0000000..fc55fd7
--- /dev/null
+++ b/src/main/scala/practise8/demo/Demo3FlatMap.scala
@@ -0,0 +1,12 @@
+package practise8.demo
+
+/*
+* flatMap
+* flatMap 可以粗略理解成：先 map，再把结果展开一层。*/
+object Demo3FlatMap {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3)
+    val result = nums.flatMap(x => List(x, x * 10))
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/demo/Demo4MapVsFlatMap.scala b/src/main/scala/practise8/demo/Demo4MapVsFlatMap.scala
new file mode 100644
index 0000000..6445ce8
--- /dev/null
+++ b/src/main/scala/practise8/demo/Demo4MapVsFlatMap.scala
@@ -0,0 +1,13 @@
+package practise8.demo
+
+/*
+* map 和 flatMap 对比*/
+object Demo4MapVsFlatMap {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3)
+
+    println(nums.map(x => List(x, x + 10))) // 结构保持
+
+    println(nums.flatMap(x => List(x, x + 10))) // 展开一层
+  }
+}
diff --git a/src/main/scala/practise8/demo/Demo5SplitFlatMap.scala b/src/main/scala/practise8/demo/Demo5SplitFlatMap.scala
new file mode 100644
index 0000000..53ea8bf
--- /dev/null
+++ b/src/main/scala/practise8/demo/Demo5SplitFlatMap.scala
@@ -0,0 +1,20 @@
+package practise8.demo
+
+/*
+* split + flatMap 拆分字符串*/
+object Demo5SplitFlatMap {
+  def main(args: Array[String]): Unit = {
+    val sentences = List(
+      "hello scala",
+      "hello spark"
+    )
+
+    // 使用map
+    val result = sentences.map(x => x.split(" ").toList)
+    println(result)
+
+    // 使用flatMap
+    val result2 = sentences.flatMap(x => x.split(" "))
+    println(result2)
+  }
+}
diff --git a/src/main/scala/practise8/demo/Demo6WordsFlatMap.scala b/src/main/scala/practise8/demo/Demo6WordsFlatMap.scala
new file mode 100644
index 0000000..1b276ee
--- /dev/null
+++ b/src/main/scala/practise8/demo/Demo6WordsFlatMap.scala
@@ -0,0 +1,14 @@
+package practise8.demo
+
+/*
+* map 和 flatMap 对比*/
+object Demo6WordsFlatMap {
+  def main(args: Array[String]): Unit = {
+    val words = List("a b", "c d")
+    val mapWords = words.map(_.split(" ").toList)
+    println(mapWords)
+
+    val flatMapWords = words.flatMap(_.split(" ").toList)
+    println(flatMapWords)
+  }
+}
diff --git a/src/main/scala/practise8/exercises/Exercises1.scala b/src/main/scala/practise8/exercises/Exercises1.scala
new file mode 100644
index 0000000..893e694
--- /dev/null
+++ b/src/main/scala/practise8/exercises/Exercises1.scala
@@ -0,0 +1,28 @@
+package practise8.exercises
+
+/*
+* 练习 1：map 产生嵌套集合
+
+给：
+val nums = List(1, 2, 3)
+
+使用：
+map
+
+让每个数字变成：
+List(x, x * 10)
+
+最终结果：
+List(
+  List(1,10),
+  List(2,20),
+  List(3,30)
+)
+* */
+object Exercises1 {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3)
+    val result = nums.map(x => List(x, x * 10))
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/exercises/Exercises2.scala b/src/main/scala/practise8/exercises/Exercises2.scala
new file mode 100644
index 0000000..6bf2ab7
--- /dev/null
+++ b/src/main/scala/practise8/exercises/Exercises2.scala
@@ -0,0 +1,21 @@
+package practise8.exercises
+
+/*
+* 练习 2：flatMap
+
+还是：
+val nums = List(1, 2, 3)
+
+使用 flatMap：
+每个数字变成 List(x, x * 10)
+
+最终：
+List(1,10,2,20,3,30)
+* */
+object Exercises2 {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3)
+    val result = nums.flatMap(x => List(x, x * 10))
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/exercises/Exercises3.scala b/src/main/scala/practise8/exercises/Exercises3.scala
new file mode 100644
index 0000000..36daa60
--- /dev/null
+++ b/src/main/scala/practise8/exercises/Exercises3.scala
@@ -0,0 +1,24 @@
+package practise8.exercises
+
+/*
+* 练习 3：平方展开
+
+给：
+val nums = List(1, 2, 3, 4)
+
+使用：
+flatMap
+
+让每个数字变成：
+List(x, x * x)
+
+最终：
+List(1,1,2,4,3,9,4,16)
+* */
+object Exercises3 {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3, 4)
+    val result = nums.flatMap(x => List(x, x * x))
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/exercises/Exercises4.scala b/src/main/scala/practise8/exercises/Exercises4.scala
new file mode 100644
index 0000000..6a86840
--- /dev/null
+++ b/src/main/scala/practise8/exercises/Exercises4.scala
@@ -0,0 +1,30 @@
+package practise8.exercises
+
+/*
+* 练习 4：字符串拆分
+
+给：
+val sentences = List(
+  "hello scala",
+  "hello spark"
+)
+
+使用：
+flatMap
+
+将它拆成：
+List(hello, scala, hello, spark)
+
+提示：
+_.split(" ")
+* */
+object Exercises4 {
+  def main(args: Array[String]): Unit = {
+    val sentences = List(
+      "hello scala",
+      "hello spark"
+    )
+    val result = sentences.flatMap(_.split(" "))
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise8/exercises/Exercises5.scala b/src/main/scala/practise8/exercises/Exercises5.scala
new file mode 100644
index 0000000..6df65af
--- /dev/null
+++ b/src/main/scala/practise8/exercises/Exercises5.scala
@@ -0,0 +1,33 @@
+package practise8.exercises
+/*
+* 练习 5 ⭐
+
+给：
+val nums = List(1, 2, 3, 4, 5)
+
+使用 flatMap：
+偶数 → 保留
+奇数 → 丢弃
+偶数 x → 生成 List(x, x * 10)
+
+最终：
+List(2, 20, 4, 40)
+
+提示：这里可以利用：
+if
+
+例如：
+if (...) {
+  List(...)
+} else {
+  List()
+}*/
+object Exercises5 {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3, 4, 5)
+    val result = nums
+      .filter(_ % 2 ==0)
+      .flatMap(x=>List(x,x*10))
+    println(result)
+  }
+}