|NO.Z.00051|——————————|BigDataEnd|——|Hadoop&Scala.V07|——|Scala.v07|模式匹配和样例类|Option|模式匹配|

一、Option与模式匹配

### --- Option与模式匹配

~~~     Scala Option选项类型用来表示一个值是可选的，有值或无值。
~~~     Option[T] 是一个类型为 T 的可选值的容器，可以通过get()函数获取Option的值。如果值存在，
~~~     Option[T] 就是一个 Some。如果不存在，Option[T] 就是对象 None 。
~~~     Option通常与模式匹配结合使用，用于判断某个变量是有值还是无值。

### --- 编程示例

object OptionMatch {
    val grades = Map("jacky" -> 90, "tom" -> 80, "jarry" -> 95)
    def getGrade(name: String): Unit = {
        val grade = grades.get(name)
        grade match {
            case Some(grade) => println("成绩：" + grade)
            case None => println("没有此人成绩！")
        }
}
def main(args: Array[String]): Unit = {
    getGrade("jacky")
    getGrade("张三")
}
}

二、编程实现

### --- 编程代码

package yanqi.cn.part07

object OptionDemo {
  val grades = Map("jacky" -> 90, "tom" -> 80, "jarry" -> 60)

  def getGrade(name: String): Unit = {
    val grade: Option[Int] = grades.get(name)
    grade match {
      case Some(grade) => println("成绩是：" + grade)
      case None => println("没有此人成绩！")
    }
  }

  def main(args: Array[String]): Unit = {
    getGrade("jacky")
    getGrade("lisi")
  }
}

### --- 编译打印

D:\JAVA\jdk1.8.0_231\bin\java.exe "-javaagent:D:\IntelliJIDEA\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar=57934:D:\IntelliJIDEA\IntelliJ IDEA 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath D:\JAVA\jdk1.8.0_231\jre\lib\charsets.jar;D:\JAVA\jdk1.8.0_231\jre\lib\deploy.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\access-bridge-64.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\cldrdata.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\dnsns.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\jaccess.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\jfxrt.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\localedata.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\nashorn.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunec.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunjce_provider.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunmscapi.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\sunpkcs11.jar;D:\JAVA\jdk1.8.0_231\jre\lib\ext\zipfs.jar;D:\JAVA\jdk1.8.0_231\jre\lib\javaws.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jce.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jfr.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jfxswt.jar;D:\JAVA\jdk1.8.0_231\jre\lib\jsse.jar;D:\JAVA\jdk1.8.0_231\jre\lib\management-agent.jar;D:\JAVA\jdk1.8.0_231\jre\lib\plugin.jar;D:\JAVA\jdk1.8.0_231\jre\lib\resources.jar;D:\JAVA\jdk1.8.0_231\jre\lib\rt.jar;E:\NO.Z.10000——javaproject\NO.Z.00002.Hadoop\ScalaPro\out\production\ScalaPro;D:\JAVA\scala-2.12.2\lib\scala-library.jar;D:\JAVA\scala-2.12.2\lib\scala-reflect.jar yanqi.cn.part07.OptionDemo
成绩是：90
没有此人成绩！

Process finished with exit code 0

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Walter Savage Landor:strove with none,for none was worth my strife.Nature I loved and, next to Nature, Art:I warm'd both hands before the fire of life.It sinks, and I am ready to depart

                                                                                                                                                   ——W.S.Landor

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