java基础-引用

分类：强引用（Strong Reference）、软引用（Soft Reference）、若引用(Weak Reference)、虚引用(Phantom Reference)

强引用 

　　java默认引用方式，只要引用链存在，系统哪怕OOM都不会回收

软引用 SoftReference<T>

　　SoftReference<T> 内存不足时 gc运行就会回收

弱引用 WeakReference<T>

　　WeakReference<T> 只要gc运行就会被回收

虚引用 

　　虚引用 需要配合ReferenceQueue使用  get的是null  需要ReferenceQueue.pull()

 

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class ReferenceDemo {       @Test     fun ReferenceTest() {         //强引用         val user = UserInfo()//这个就是强引用 只要引用链存在就不会被回收         val softUser by Soft { UserInfo(name = "softUser", age = 1) }//软引用 内存不足才gc回收         val weakUser by Weak { UserInfo(name = "weakUser", age = 2) } //若引用 只要gc回收就会被回收           println("before gc")         println("user is ${user}")         println("softUser is ${softUser}")         println("weakUser is ${weakUser}")         System.gc()         println("after gc")         println("user is ${user}")         println("softUser is ${softUser}")         println("weakUser is ${weakUser}")           val list = LinkedList<Byte>()         try {             (0..100).forEach { _ ->                 list.add((1024 * 1024 * 10).toByte())             }         } catch (e: Throwable) {             e.printStackTrace()         }finally {             println("after big size")             println("user is ${user}")             println("softUser is ${softUser}")             println("weakUser is ${weakUser}")         }           //        输出结果 //        before gc //                user is com.tab.composedemo.UserInfo@c03cf28 //        softUser is com.tab.composedemo.UserInfo@1329eff //        weakUser is com.tab.composedemo.UserInfo@6497b078 //        after gc //                user is com.tab.composedemo.UserInfo@c03cf28 //        softUser is com.tab.composedemo.UserInfo@1329eff //        weakUser is null       } }   class UserInfo(var name: String = "", var age: Int = 1)   class Weak<T>(initializer: () -> T?) {     private var reference: WeakReference<T?> = WeakReference(initializer())       constructor() : this({ null })       operator fun getValue(thisRef: Any?, property: KProperty<*>): T? = reference.get()       operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) {         this.reference = WeakReference(value)     } }     class Soft<T>(initializer: () -> T?) {     private var reference: SoftReference<T?> = SoftReference(initializer())       constructor() : this({ null })       operator fun getValue(thisRef: Any?, property: KProperty<*>): T? = reference.get()       operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) {         this.reference = SoftReference(value)     } }

　　

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