diff --git a/src/main/scala/practise3/comprehensive/Comprehensive.scala b/src/main/scala/practise3/comprehensive/Comprehensive.scala
new file mode 100644
index 0000000..9adc5d2
--- /dev/null
+++ b/src/main/scala/practise3/comprehensive/Comprehensive.scala
@@ -0,0 +1,32 @@
+package practise3.comprehensive
+
+/*综合题 ⭐
+
+给你：
+val scores = List(55, 60, 72, 85, 91, 96)
+
+完成：
+第一步
+使用 filter：
+只保留 >= 60
+得到：
+List(60, 72, 85, 91, 96)
+第二步
+使用 map：
+每个成绩 + 5
+得到：
+List(65, 77, 90, 96, 101)
+也就是说最终写出类似：
+val result = scores
+  .filter(...)
+.map(...)
+println(result)*/
+object Comprehensive {
+  def main(args: Array[String]): Unit = {
+    val scores = List(55, 60, 72, 85, 91, 96)
+    val result = scores
+      .filter(x => x >= 60)
+      .map(x => x + 5)
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise3/demo/Demo1DefAndFunction.scala b/src/main/scala/practise3/demo/Demo1DefAndFunction.scala
new file mode 100644
index 0000000..097c31c
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo1DefAndFunction.scala
@@ -0,0 +1,13 @@
+package practise3.demo
+/*
+def 方法 vs => 函数值
+*/
+object Demo1DefAndFunction {
+  def main(args: Array[String]): Unit = {
+    def DefAdd(a: Int, b: Int): Int = a + b //这是一个方法
+    val ValAdd = (a: Int, b: Int) => a + b //这是一个函数值
+    println(DefAdd(10, 20))
+    println(ValAdd(10, 20))
+  }
+
+}
diff --git a/src/main/scala/practise3/demo/Demo2FunctionLiteral.scala b/src/main/scala/practise3/demo/Demo2FunctionLiteral.scala
new file mode 100644
index 0000000..5de9e52
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo2FunctionLiteral.scala
@@ -0,0 +1,11 @@
+package practise3.demo
+/*
+* => 匿名函数语法
+* */
+object Demo2FunctionLiteral {
+  def main(args: Array[String]): Unit = {
+    val f = (a: Int) => a * 2 //本质是输入一个数字 ➡️ 乘以 2 ➡️ 得到结果
+    println(f(10))
+  }
+
+}
diff --git a/src/main/scala/practise3/demo/Demo3FunctionVariable.scala b/src/main/scala/practise3/demo/Demo3FunctionVariable.scala
new file mode 100644
index 0000000..3c657a8
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo3FunctionVariable.scala
@@ -0,0 +1,13 @@
+package practise3.demo
+/*
+* 函数赋值给变量
+* */
+object Demo3FunctionVariable {
+  def main(args: Array[String]): Unit = {
+    val age = 20 // 普通变量
+    val name = "Tom" // 字符串
+    val double = (x: Int) => x * 2 // 函数也可以
+
+    println(double(5)) // 此时double不是一个数字，而是一个“函数”。
+  }
+}
diff --git a/src/main/scala/practise3/demo/Demo4FunctionType.scala b/src/main/scala/practise3/demo/Demo4FunctionType.scala
new file mode 100644
index 0000000..e764681
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo4FunctionType.scala
@@ -0,0 +1,16 @@
+package practise3.demo
+/*
+* 函数类型 Int => Int
+* */
+object Demo4FunctionType {
+  def main(args: Array[String]): Unit = {
+    val double = (x: Int) => x * 2  // 这个函数可以理解成Int => Int
+
+    val double2: Int => Int = (x: Int) => x * 2  // 接收一个 Int，返回一个 Int。
+    val double3: Int => Int = x => x * 2 // 再简化
+
+    println(double(2))
+    println(double2(2))
+    println(double3(2))
+  }
+}
diff --git a/src/main/scala/practise3/demo/Demo5MultiParameterFunction.scala b/src/main/scala/practise3/demo/Demo5MultiParameterFunction.scala
new file mode 100644
index 0000000..6606c32
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo5MultiParameterFunction.scala
@@ -0,0 +1,11 @@
+package practise3.demo
+/*
+* 多参数函数
+* */
+object Demo5MultiParameterFunction {
+  def main(args: Array[String]): Unit = {
+    val add = (a: Int, b: Int) => a + b // 它的函数类型是(Int, Int) => Int
+
+    println(add(10, 20))
+  }
+}
diff --git a/src/main/scala/practise3/demo/Demo6Map.scala b/src/main/scala/practise3/demo/Demo6Map.scala
new file mode 100644
index 0000000..7ca24fc
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo6Map.scala
@@ -0,0 +1,36 @@
+package practise3.demo
+/*
+* map 基本使用
+* */
+object Demo6Map {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3, 4, 5)
+    /*
+    * 普通 Java 思维可能是：
+    * 遍历 List
+    *
+    *  取出一个元素
+    *  ⬇️
+    *  乘 2
+    *  ⬇️
+    *  放到新 List
+    * */
+
+    val result = nums.map(x => x * 2) // scala直接，对 nums 中的每一个元素，都执行一次 x => x * 2
+    /*
+    *  nums
+    *    ⬇
+    *   map
+    *    ⬇
+    *   给 map 一个函数
+    *    ⬇
+    *   x => x * 2
+    */
+    val result2 = nums.map(x=>x)
+    val result3 = (x:Int) => x * 2
+
+    println(result)
+    println(result2)
+    println(result3(2))
+  }
+}
diff --git a/src/main/scala/practise3/demo/Demo7FunctionAsParameter.scala b/src/main/scala/practise3/demo/Demo7FunctionAsParameter.scala
new file mode 100644
index 0000000..284ab3f
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo7FunctionAsParameter.scala
@@ -0,0 +1,16 @@
+package practise3.demo
+/*
+* 匿名函数与函数变量
+* */
+object Demo7FunctionAsParameter {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3, 4, 5)
+    val result =nums.map(x => x * 2)
+
+    val double = (x: Int) => x * 2
+    val result2 = nums.map(double)
+
+    println(result)
+    println(result2)
+  }
+}
diff --git a/src/main/scala/practise3/demo/Demo8Filter.scala b/src/main/scala/practise3/demo/Demo8Filter.scala
new file mode 100644
index 0000000..9ec86ca
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo8Filter.scala
@@ -0,0 +1,26 @@
+package practise3.demo
+/*
+* filter 基本使用
+* */
+object Demo8Filter {
+  def main(args: Array[String]): Unit = {
+    /*
+    * map 是“每一个都处理”。
+    * 那么我只想留下符合条件的数据怎么办？
+    *
+    */
+    val nums = List(1, 2, 3, 4, 5)
+
+    val result = nums.filter(x => x >= 3)
+
+    println(result)
+
+    /*
+    * 1 → false → 丢掉
+    * 2 → false → 丢掉
+    * 3 → true  → 保留
+    * 4 → true  → 保留
+    * 5 → true  → 保留
+    */
+  }
+}
\ No newline at end of file
diff --git a/src/main/scala/practise3/demo/Demo9MapAndFilter.scala b/src/main/scala/practise3/demo/Demo9MapAndFilter.scala
new file mode 100644
index 0000000..122b25f
--- /dev/null
+++ b/src/main/scala/practise3/demo/Demo9MapAndFilter.scala
@@ -0,0 +1,14 @@
+package practise3.demo
+/*
+* map 与 filter 对比
+* */
+object Demo9MapAndFilter {
+  def main(args: Array[String]): Unit = {
+    println(List(1, 2, 3).map(x => x * 10))  // List(10, 20, 30)
+    println(List(1, 2, 3).filter(x => x >= 2)) // List(2, 3)
+    /*
+    * map    → 改造元素
+    *filter → 筛选元素
+    */
+  }
+}
diff --git a/src/main/scala/practise3/exercises/Exercises1.scala b/src/main/scala/practise3/exercises/Exercises1.scala
new file mode 100644
index 0000000..75daf47
--- /dev/null
+++ b/src/main/scala/practise3/exercises/Exercises1.scala
@@ -0,0 +1,28 @@
+package practise3.exercises
+/*
+* 练习 1：创建一个函数
+
+创建：
+double
+
+要求：
+输入 10
+输出 20
+
+也就是：
+println(double(10))
+
+得到：
+20
+
+要求使用：
+=>
+而不是 def。
+*/
+object Exercises1 {
+  def main(args: Array[String]): Unit = {
+    val double = (x:Int) => x * 2
+
+    println(double(10))
+  }
+}
diff --git a/src/main/scala/practise3/exercises/Exercises2.scala b/src/main/scala/practise3/exercises/Exercises2.scala
new file mode 100644
index 0000000..840b9f9
--- /dev/null
+++ b/src/main/scala/practise3/exercises/Exercises2.scala
@@ -0,0 +1,21 @@
+package practise3.exercises
+
+/*练习 2：创建平方函数
+
+创建：
+square
+
+要求：
+println(square(5))
+
+得到：
+25
+
+要求写成：
+val square = ...*/
+object Exercises2 {
+  def main(args: Array[String]): Unit = {
+    val square = (x: Int) => x * x
+    print(square(5))
+  }
+}
diff --git a/src/main/scala/practise3/exercises/Exercises3.scala b/src/main/scala/practise3/exercises/Exercises3.scala
new file mode 100644
index 0000000..6d4c1bc
--- /dev/null
+++ b/src/main/scala/practise3/exercises/Exercises3.scala
@@ -0,0 +1,21 @@
+package practise3.exercises
+
+/*练习 3：两个参数的函数
+
+创建：
+add
+
+要求：
+println(add(10, 20))
+
+输出：
+30
+
+函数类型最好也写出来：
+val add: (Int, Int) => Int = ...*/
+object Exercises3 {
+  def main(args: Array[String]): Unit = {
+    val add = (x: Int, y: Int) => x + y
+    println(add(10, 20))
+  }
+}
diff --git a/src/main/scala/practise3/exercises/Exercises4.scala b/src/main/scala/practise3/exercises/Exercises4.scala
new file mode 100644
index 0000000..085feff
--- /dev/null
+++ b/src/main/scala/practise3/exercises/Exercises4.scala
@@ -0,0 +1,15 @@
+package practise3.exercises
+/*练习 4：使用 map
+
+给你
+val nums = List(1, 2, 3, 4, 5)
+
+使用 map，得到：
+List(2, 4, 6, 8, 10)*/
+object Exercises4 {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3, 4, 5)
+    val result = nums.map(x => x*2)
+    println(result)
+  }
+}
diff --git a/src/main/scala/practise3/exercises/Exercises5.scala b/src/main/scala/practise3/exercises/Exercises5.scala
new file mode 100644
index 0000000..d306066
--- /dev/null
+++ b/src/main/scala/practise3/exercises/Exercises5.scala
@@ -0,0 +1,19 @@
+package practise3.exercises
+
+/*练习 5：使用 filter
+
+给你：
+val nums = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+
+使用 filter，只保留偶数：
+List(2, 4, 6, 8, 10)
+
+提示：
+x % 2 == 0*/
+object Exercises5 {
+  def main(args: Array[String]): Unit = {
+    val nums = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+    val result = nums.filter(x => x % 2 == 0)
+    println(result)
+  }
+}