定义的对象如下
object Conversions {
def inchesToCentimeters( inch: Double ): Double = {
inch * 2.54
}
def gallonsToLiters( gallon: Double ): Double = {
gallon * 3.78541178
}
def milesToKilometers( mile: Double ): Double = {
mile * 1.609344
}
}
使用扩展方式重新实现的类/对象代码如下
class UnitConversion( base: Double ) {
def apply( from: Double ): Double = {
from * base
}
}
object InchesToCentimeters extends UnitConversion( 2.54 )
object GallonsToLiters extends UnitConversion(3.78541178)
object MilesToKilometers extends UnitConversion(1.609344)
扩展对象代码为
object Origin extends java.awt.Point()
java.awt.Point 类不是一个抽象类或Interface，其中包含了 x,y 变量和相关操作，对象内容是可变的
定义的 Point 类及其伴生类如下
class Point( var x:Double = 0, var y: Double = 0 ) {
override def toString(): String = {
"(%f,%f)".format( x, y )
}
}
object Point {
def apply( x: Double, y: Double ) = {
new Point( x, y )
}
}
应用程序如下
object Reverse extends App {
println(args.reverse.mkString(" "))
}
定义的枚举如下
object PlayCard extends Enumeration {
type Suit = Value
val Heart = Value( "♥" )
val Diamond = Value( "♦" )
val Spade = Value( "♠" )
val Club = Value( "♣" )
}
同上，对象内新增函数 isRed
class PlayCard( val suit: PlayCard.Suit.Suit, val value: Char ) {
override def toString() = {
"%s%s".format( suit, value )
}
}
object PlayCard {
object Suit extends Enumeration {
type Suit = Value
val Heart = Value( "♥" )
val Diamond = Value( "♦" )
val Spade = Value( "♠" )
val Club = Value( "♣" )
}
import PlayCard._
def isRed( c: PlayCard ): Boolean = {
c.suit == Suit.Heart || c.suit == Suit.Diamond
}
}
代码如下
object Color extends Enumeration {
type Color = Value
val black = Value( 0x000000 )
val red = Value( 0xff0000 )
val green = Value( 0x00ff00 )
val blue = Value( 0x0000ff )
val white = Value( 0xffffff )
val yellow= Value( 0xffff00 )
val cyan = Value( 0x00ffff )
val magenta = Value( 0xff00ff )
}