大数据之脚踏实地学12--Scala数据类型与运算符

// 定义val变量
scala> val name = "刘顺祥"
name: String = 刘顺祥

scala> name = "xuxin"  // 不可以重新赋值
<console>:12: error: reassignment to val
       name = "xuxin"
            ^

// 定义var变量
scala> var age:Int = 30
age: Int = 30

scala> age = 28  // var定义的变量，可以重新赋值
age: Int = 28

// 多个变量赋予同一个数值
val x1,x2 : Int = 10

scala> val mybyte : Byte = 124
mybyte: Byte = 124

scala> val mybyte2 : Byte = 321  // 超过Byte的数值范围，会报错
<console>:11: error: type mismatch;
 found   : Int(321)
 required: Byte
       val mybyte2 : Byte = 321  // 超过Byte的数值范围，会报错
                            ^

scala> val myInt : Int = 1234567 // 对于一个整数，默认为Int型
myInt: Int = 1234567

scala> val myLong : Long = 12345678910L // 必须在整数的末尾加上字母l或L，否则溢出
myLong: Long = 12345678910

scala> val myDouble : Double = 3.14159 // 对于一个实数，默认为双精度浮点型
myDouble: Double = 3.14159

scala> val myFloat : Float = 3.14159f // 必须在实数的末尾加上字母f或F
myFloat: Float = 3.14159

scala> val myChar : Char = 'A'
myChar: Char = A

scala> val myString : String = "今天天气很好！"
myString: String = 今天天气很好！

scala> val myBoolean : Boolean = true
myBoolean: Boolean = true

scala> val x1 : Byte = 123
x1: Byte = 123
scala> x1 + 100  // Byte + Int 会自动升级为Int
res0: Int = 223

scala> val x2 : Int = 10000
x2: Int = 10000
scala> x2 + 1111.1  // Int + Double 会自动升级为Double
res1: Double = 11111.1

scala> val x3 : Char = 'A'
x3: Char = A
scala> x3 + 1  // Char + Int 会自动升级为Int
res2: Int = 66

scala> val x4 : Short = x1 + 100   // Int + Int 无法降级到Short，故报错
<console>:12: error: type mismatch;
 found   : Int
 required: Short
       val x4 : Short = x1 + 100   // Int + Int 无法降级到Short，故报错

scala> val x4 : Short = (x1 + 100).toShort  // toShort方法强制转换为Short类型
x4: Short = 223

scala> (x3 + 1).toChar  // 将Int型的66强制转换为Char类型
res3: Char = B

scala> (23.5/5).toInt  // 将Double类型强制转换为Int类型
res5: Int = 4

object CompareOprate {
   def main(args: Array[String]) : Unit =  {
      var a = 18;
      var b = 8;

      println("a = " + a + ", b = " + b)
      println("a >= b = " + (b >= a))
      println("a < b = " + (a < b))
      println("a == b = " + (a == b))
      println("a != b = " + (a != b))
      println("a >= b || a < 10 = " + (a >= b || a < 10))
      println("!(a <= b) = " + !(a <= b))
   }
}

[root@hadoop char01]# scalac CompareOprate.scala  //编译Scala脚本
[root@hadoop char01]# scala CompareOprate  // 运行编译后的文件
a = 18, b = 8
a >= b = false
a < b = false
a == b = false
a != b = true
a >= b || a < 10 = true
!(a <= b) = true

object MathOprate {
   def main(args: Array[String]) : Unit = {
   var  a = 23
   val  b = 6
   println("a="+a + " ,b="+b) // 打印a和b的值
   println("a + b =" + (a + b)) // 加法运算
   println("a - b =" + (a - b)) // 减法运算
   println("a * b =" + (a * b)) // 乘法运算
   println("a / b =" + (a / b)) // 除法运算（两个整数的商）
   println("a * 1.0 / b =" + (a*1.0 / b)) // 除法运算（浮点数与整数的商）
   println("a % b =" + (a % b)) // 余数运算

   var c = a
   c += 10 // 自加运算
   println("a += 10 = " + c) // 式子中的加号为字符串的拼接运算
        }
}

[root@hadoop char01]# scalac MathOprate.scala  //编译Scala脚本
[root@hadoop char01]# scala MathOprate  // 运行编译后的文件
a=23 ,b=6
a + b =29
a - b =17
a * b =138
a / b =3
a * 1.0 / b =3.8333333333333335
a % b =5
a += 10 = 33