kotlin中ByteArray和Array 之間的區別
[英]Difference between ByteArray and Array in kotlin
I don't understand why e.g. the java.security.MessageDigest.digest() method which is declared as returning byte[] in Java returns a ByteArray in Kotlin although Kotlin usually seems to call byte[] an Array<Byte>.
我不明白為什么，例如在Java中聲明為返回byte []的java.security.MessageDigest.digest（）方法返回Kotlin中的ByteArray，盡管Kotlin通常似乎將byte []稱為Array
E.g. the following does not work:
例如。以下不起作用：
fun main(args : Array<String>) {
val md = java.security.MessageDigest.getInstance("SHA")
if (md == null) throw NullPointerException()
val result : Array<Byte>? = md.digest()
}
Type mismatch: inferred type is ByteArray? but Array<Byte>? was expected
類型不匹配：推斷類型是ByteArray？但是數組
2 个解决方案
#1
27
Due to Java's limitations, Kotlin has 9 array types: Array<...> for arrays of references (in the JVM sense) and 8 specialized array types, i.e. IntArray, ByteArray etc.
由於Java的限制，Kotlin有9種數組類型：Array <...>用於引用數組（在JVM意義上）和8種專用數組類型，即IntArray，ByteArray等。
https://kotlinlang.org/docs/reference/java-interop.html#java-arrays
https://kotlinlang.org/docs/reference/java-interop.html#java-arrays
The main reason for this distinction is performance: if we didn't specialize arrays it'd lead to a lot of boxing/unboxing and make arrays slow. This would be unacceptable because the only reason one might want to prefer arrays over collections is performance.
這種區別的主要原因是性能：如果我們沒有專門化數組，它會導致大量的裝箱/拆箱並使陣列變慢。這是不可接受的，因為人們可能希望更喜歡數組而不是集合的唯一原因是性能。
#2
6
Said in short, just for future reference.
簡而言之，僅供將來參考。
ByteArray equals byte[] in Java
Array<Byte> equals Byte[] in JavaByteArray等於Java Array
中的byte []等於Java中的Byte []
No benefit from using one over the other in Kotlin, only if the code is to be parsed to Java.
只有在將代碼解析為Java時，才能在Kotlin中使用其中一個。
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