add ScalaAdvance/ContextBound1/, update implicit demo, readme

README.md

@@ -490,7 +490,7 @@
 	- [Implicit_Demo1](./src/main/scala/ScalaBasic/Implicit_Demo1.scala)
 	- [Implicit_Demo2](./src/main/scala/ScalaBasic/Implicit_Demo2.scala)
 	- [Implicit_Demo3](./src/main/scala/ScalaBasic/Implicit_Demo3.scala)
-	- [Implicit_Demo4](./src/main/scala/ScalaBasic/Implicit_Demo4.scala)
+	- [Implicit_Demo4](./src/main/scala/ScalaBasic/Implicit_Demo4.scala) : implicit parameter
 	- [Implicit_Demo5](./src/main/scala/ScalaBasic/Implicit_Demo5.scala)
 	- [Implicit_Demo6](./src/main/scala/ScalaBasic/Implicit_Demo6.scala)
 	- [Implicit_Demo7](./src/main/scala/ScalaBasic/Implicit_Demo7.scala)

src/main/scala/ScalaAdvance/ContextBound1/demo1.scala

@@ -0,0 +1,67 @@
+package ScalaAdvance.ContextBound1
+
+// https://www.bilibili.com/video/BV12N411R726?p=280
+
+/**
+ *   Context bounds demo 1 :
+ *
+ *     1) similar as view bounds, context bounds is also a `language sugar` of implicit parameters
+ *
+ *
+ *  Note : Difference between `Ordered` and `Ordering`:
+ *
+ *        -> Ordered : inherits from java's Comparable interface,
+ *                     Comparable is an "internal" comparator, override CompareTo method
+ *
+ *        -> Ordering : inherits from java's Comparator interface,
+ *                      Comparator is an "external" comparator, (need to implement a class for it)
+ *
+ */
+
+object demo1 {
+
+  // here we define a implicit value
+  // ref : https://github.com/yennanliu/utility_Scala/blob/master/src/main/scala/ScalaBasic/Implicit_Demo4.scala
+  implicit val personComparator = new Ordering[Person]{
+    override def compare(p1: Person, p2: Person): Int = {
+      p1.age - p2.age
+    }
+  }
+
+  // entry point
+  def main(args: Array[String]): Unit = {
+
+    // -------------------
+    // demo 1
+    // -------------------
+    val p1 = new Person("JAY",19)
+    val p2 = new Person("lynn",20)
+    val compareComm4 = new CompareComm4(p1, p2)
+    println(compareComm4.getter)
+
+  }
+}
+
+// a simple Person class
+class Person(val name:String, val age:Int) {
+  // method
+  override def toString: String = {
+    this.name + "\t" + this.age
+  }
+}
+
+/**
+ *   Approach 1)
+ *
+ *   1) [T:Ordering] : generic type
+ *   2) accept T type object
+ *   3) implicit comparator:Ordering[T] : implicit parameter
+ *          -> if there is any obj with type Ordering[T] in code, then such obj will be sent to this class automatically
+ */
+class CompareComm4[T:Ordering](obj1:T, obj2:T)(implicit comparator:Ordering[T]){
+  def getter = {
+    if (comparator.compare(obj1, obj2) > 0 ){
+      obj1
+    }else obj2
+  }
+}

src/main/scala/ScalaBasic/Implicit_4.scala

@@ -2,6 +2,13 @@ package ScalaBasic
 
 // https://www.youtube.com/watch?v=smtulYDn7OU&list=PLmOn9nNkQxJEqCNXBu5ozT_26xwvUbHyE&index=172
 
+/**
+ *  Implicit Demo 4 :
+ *
+ *  1) implicit parameter
+ */
+
+
 object Implicit_4 extends App {
   // run
   val db1 = new DB1(new MySql1)
@@ -14,7 +21,6 @@ object Implicit_4 extends App {
    *
    *  1) will make a .class implicitClass$DB1$2 under the hood
    *  2) and also make a method : DB1$1 // via implicitClass$DB1$2 constructor, return implicit class instance
-   *
    */
   // implicit class
   implicit class DB1(val m: MySql1) {