Kotlin拳击，无法理解其中的区别吗? [英] Kotlin boxing, Can't understand the difference?

问题描述

val a: Int = 100
val boxedA: Int? = a
val anotherBoxedA: Int? = a

val b: Int = 10000
val boxedB: Int? = b
val anotherBoxedB: Int? = b

println(boxedA === anotherBoxedA) // true
println(boxedB === anotherBoxedB) // false

我不明白的是 boexA === andotherBoxedA 和 boexB === andotherBoxedB

更令人困惑的是，当更改为b t0 100时，输出为true

and more confusion is when change b t0 100 the output is true true

val a: Int = 100
val boxedA: Int? = a
val anotherBoxedA: Int? = a

val b: Int = 100
val boxedB: Int? = b
val anotherBoxedB: Int? = b

println(boxedA === anotherBoxedA) // true
println(boxedB === anotherBoxedB) // true

所以，我需要对此代码进行解释.

so, please I need explanation for this code.

推荐答案

因此，当优化时，-128到127范围内的Integer值将被缓存，而其他任何对象都具有与缓存的值相似的值，则它将得到缓存的值(类似于字符串池)所以当val a:Int = 100然后val boxedA:Int?= a，那么这里发生的是创建一个值为100的Integer对象，那么当val anotherBoxedA:Int时呢?= a，某事创建了一个对象，但是请稍等，如果它保持相同的值100，并且该值在-128到127的范围内，则anotherBoxedA将获得与boxedA相同的引用所以当boxedA === anotherBoxedA会产生true

So, as an optimization Integer values in -128 to 127 range get cached and any other object hold similar value to a cached one it will get a reference of the cached value (similar to string pool) so when val a:Int = 100 and then val boxedA :Int? = a, so what happened here is an Integer object got created with the value 100, so when val anotherBoxedA :Int? = a, the something an object got created, but wait, if it will hold the same value which is 100 and the value is in range -128 to 127 so anotherBoxedA will get the same reference as boxedA so when boxedA === anotherBoxedA will produce true

另一方面，b = 10000，它大于缓存范围(-128:127)，因此boxedB = b将创建一个新的Integer对象，anotherBoxedB = b将再次创建一个新对象，因此(boxedB === anotherBoxedB)将产生false

on the other hand b=10000 which is larger than the cache range (-128 : 127) so boxedB = b will create a new Integer object , anotherBoxedB = b will again create a new object , so (boxedB === anotherBoxedB) will produce false

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