package com.liao.day05

class CmpInt(a:Int,b:Int){

  def bigger()={
    if (a>b) a
    else b
  }
}

/*
*   上界(Upper Bonds):
*   <:
*   相当于这个T是Comparable的子类
*/
class CmpComm1[T <: Comparable[T]](o1:T,o2:T){
  def bigger()={
    if (o1.compareTo(o2)>0) o1
    else o2
  }
}
/*
  *视图界定
  * <%
 */
class CmpComm2[T <% Comparable[T]](o1:T,o2:T){//T需要的是Comparable的子类
  def bigger()={
    if (o1.compareTo(o2)>0) o1
    else o2
  }
}
/**
  *
  * Ordered使用
  */
class CmpComm3[T <% Ordered[T]](o1:T,o2:T){//T需要的是Comparable的子类
  def bigger()={
    if (o1>o2) o1
    else o2
  }
}
/*学生类定义*/
class Student1(val name:String,val age:Int){
  override def toString: String = this.name+"\t"+this.age
}

class Student2(val name:String,val age:Int) extends Ordered[Student2]{
  override def compare(that: Student2): Int = this.age-that.age
  override def toString: String = this.name+"\t"+this.age
}

//比较器编写
/**
  *T:Ordering上下文界定
  */
class CmpComm4[T : Ordering](o1:T,o2:T){//T需要的是Comparable的子类
  def bigger()={
    //定义一个隐式转换比较类型
    val cmptor=implicitly[Ordering[T]]
    if(cmptor.compare(o1,o2)>0) o1 else o2
  }
}

class CmpComm5[T : Ordering](o1:T,o2:T)(implicit cmptor:Ordering[T]){
  def bigger()={
    if(cmptor.compare(o1,o2)>0) o1 else o2
  }
}

object ScalaUpperLowerBounds {
  
  def main(args: Array[String]): Unit = {

    val cmp1=new CmpInt(4,9)//scala自动帮我们做了下面的操作
    val cmp2=new CmpInt(Integer.valueOf(4),Integer.valueOf(9))
    println(cmp1.bigger())

    val long1=new CmpComm1[java.lang.Long](3L,8L)//java的long才是实现了Comparable接口
    println(long1.bigger())

    val long2=new CmpComm2[Long](9L,11L)//这个视图界定可以有自动转换
    println(long2.bigger())//这里不用显式的指定是Java的Long类型

    val long3=new CmpComm3(3.14,4.999)
    println(long3.bigger())//会自动转可比较类型
  }


  val studentA=new Student1("zhang",19)
  val studentB=new Student1("li",22)

  //隐式转换将一个普通的Student类转为---->Ordered[Student]可比较的类
  implicit def student2OrderingStudent(student: Student1)=new Ordered[Student1]{
    override def compare(that: Student1): Int = student.age-that.age
  }
  //直接比较不知道会比较什么，需要编写一个比较器
  val studentCmp1=new CmpComm4(studentA,studentB)//把student转换成Ordering的Student类
  println("================================"+studentCmp1.bigger()+"=====================================")


  val studentC=new Student1("liao",18)
  val studentD=new Student1("wang",50)
  val studentCmp2=new CmpComm5(studentC,studentD)
  println("================================"+studentCmp2.bigger()+"=====================================")
  }