单例模式

单例：希望某个类只存在一个使用的对象，而不管有多少个调用者在使用它，就是单例的概念。

package base

object Singleton extends App {
val aloneC1 = AloneObj.getAloneCInstance
val aloneC2 = AloneObj.getAloneCInstance
aloneC1.addOne
aloneC2.addOne
println(aloneC1.getPrice, aloneC2.getPrice)
}

object AloneObj {
private var aloneC: AloneC = null

def getAloneCInstance: AloneC = {

// 第一次掉用时创建实例
if (this.aloneC == null) this.aloneC = new AloneC()

this.aloneC

}

}

// 需要单例的类
class AloneC {
private var price = 0.0

def addOne = {
price += 1
}

def add(num: Double): Unit = {
price += num
}

def getPrice = price
}
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package base
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object Singleton extends App {
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val aloneC1 = AloneObj.getAloneCInstance
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val aloneC2 = AloneObj.getAloneCInstance
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aloneC1.addOne
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aloneC2.addOne
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println(aloneC1.getPrice, aloneC2.getPrice)
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}
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object AloneObj {
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private var aloneC: AloneC = null
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def getAloneCInstance: AloneC = {
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// 第一次掉用时创建实例
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if (this.aloneC == null) this.aloneC = new AloneC()
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this.aloneC
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}
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}
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// 需要单例的类
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class AloneC {
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private var price = 0.0
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def addOne = {
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price += 1
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}
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def add(num: Double): Unit = {
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price += num
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}
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def getPrice = price
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}

单例模式

原文：https://www.cnblogs.com/studyNotesSL/p/11443783.html