Kotlin单例模式(带参数和不带参数)

不带参数

1.

public class Singleton private constructor() { init { println("This ($this) is a singleton") } private object Holder { val INSTANCE = Singleton() } companion object { val instance: Singleton by lazy { Holder.INSTANCE } } var b:String? = null }

2.

public class Singleton private constructor() { init { println("This ($this) is a singleton") } companion object { val instance: = Singleton() } var b:String? = null }

带参数

class Singleton private constructor(str: String) { var string: String = str; init { println("str is $str") println("string is $string") } companion object { @Volatile var instance: Singleton? = null fun getInstance(c: String): Singleton { if (instance == null) { synchronized(Singleton::class) { if (instance == null) { instance = Singleton(c) } } } return instance!! } } }