单例模式Kotlin篇

单例模式Java篇

单例模式 - 饿汉式

/**
 *
 * @Description 饿汉式-定义一个object对象表达式即可，无需手动去设置构造器私有化和提供全局访问点
 */
object SingleTon1

单例模式-懒汉式

无参数

/**
 * @Description 懒汉式 - 无参数传入
 */
class Singleton2 private constructor() {

    companion object {
        private var INSTANCE: Singleton2? = null
            get() {
                return field ?: Singleton2()
            }

        fun getInstance(): Singleton2 {
            return INSTANCE!!
        }
    }
}

有参数

/**
 * @Description 懒汉式 - 有参数出阿努如
 */
class Singleton2Params private constructor(val context: Context) {

    companion object {
        private var INSTANCE: Singleton2Params? = null

        fun getInstance(context: Context): Singleton2Params {
            return INSTANCE ?: Singleton2Params(context)
        }
    }

}

懒汉式安全

/**
 * @Description 懒汉式安全，方法同步用 @Synchronized
 */
class Singleton3 private constructor() {

    companion object {
        private var INSTANCE: Singleton3? = null
            get() {
                return field ?: Singleton3()
            }

        @JvmStatic  // @JvmStatic 在Java中可以直接调用
        @Synchronized
        fun getInstance(): Singleton3 {
            return INSTANCE!!
        }
    }
}

单例模式-双重锁DCL

基本

/**
 * @Description DCL
 */
class Singleton4 private constructor() {
    companion object {
        @Volatile
        private var INSTANCE: Singleton4? = null
        fun getInstance(): Singleton4 {
            if (INSTANCE == null) {
                synchronized(this) {
                    if (INSTANCE == null) {
                        INSTANCE = Singleton4()
                    }
                }
            }
            return INSTANCE!!
        }
    }
 
}

by lazy 写法

/**
 * @Description DCL
 */
class Singleton4DCL private constructor() {

    companion object {
        val INSTANCE: Singleton4DCL by
        lazy(mode = LazyThreadSafetyMode.SYNCHRONIZED) {
            Singleton4DCL()
        }
    }
}

和 1 一样，换一种写法

/**
 * @Description DCL
 */
class Singleton4DCLNew private constructor() {

    companion object {
        @Volatile
        private var INSTANCE: Singleton4DCLNew? = null

        fun getInstance(): Singleton4DCLNew = INSTANCE ?: synchronized(this) {
            INSTANCE ?: Singleton4DCLNew()
            //instanceTon ?: Singleton4DCLNew().also { instanceTon = it }
            //instanceTon ?: Singleton4DCLNew().let {  it }
            //instanceTon ?: Singleton4DCLNew().run { this }
            //instanceTon ?: Singleton4DCLNew().apply { instanceTon = this }
        }
    }
}

DCL传入参数

class SingleInstance private constructor(private val mContext: Context) {

    companion object {
        @Volatile
        private var INSTANCE: SingleInstance? = null

        fun getInstance(context: Context): SingleInstance =
            INSTANCE ?: synchronized(this) {
                INSTANCE ?: SingleInstance(context)
            }
    }

    fun doSomeThing() {
        val string = mContext.resources.getString(R.string.app_name)
        Log.d("singleDcl", string)
    }

}

单例模式-枚举

/**
 * @Description  枚举单例模式
 */
enum class SingleTonEnum {
    INSTANCE;

    fun doSomething() {
        println("do some thing")
    }
}

单例模式-静态内部类

/**
 * @Description 静态内部类式
 */
class Singleton5 private constructor() {

    companion object {
        val INSTANCE: Singleton5 = Inner.INSTANCE
    }
    private object Inner {
        val INSTANCE: Singleton5 = Singleton5()
    }
}

最后编辑于：2020.08.17 10:24:36