C#和Java的泛型差異

http://www.jprl.com/Blog/archive/development/2007/Aug-31.html
雖然很舊的文章，但是很詳細的比較了C#和Java泛型的差異

最近在看Essential C# 6這本書，第11章(C# 7是在第12章)有提到Java和C#泛型機制的不同。搜尋了一些資料，小弟我大致整理如下，歡迎先進補充指正，謝謝

JDK 5加入泛型，為了避免修改JVM規格影響向下相容，是在編譯器實作泛型(不是在JVM實作)，另外Java的泛型不支援Primitive Type(等同C#的Value Type)
Java採用Code Sharing實作，對每一個泛型類或泛型方法只會生成一份object code(byte code)，Java compiler透過type erasure實作，也導致無法在runtime時期取得泛型類或泛型方法的實際型別
C#和C++ Template採用Code Specialization實作，對每一個泛型類或泛型方法都會產生一份object code
C# 2.0加入泛型，.NET是在CLI(common language implementation)加入泛型支援，性能較好，且可以在runtime時期取得泛型類或泛型方法的實際型別資訊

參考資料:
Java魔法堂：解讀基於Type Erasure的泛型
https://www.cnblogs.com/fsjohnhuang/p/4288614.html

聊聊Java泛型類型擦除及Flink類型暗示（type hint）機制
https://www.jianshu.com/p/cfb8c1386f69

Type Erasure
https://docs.oracle.com/javase/tutorial/java/generics/erasure.html

https://stackoverflow.com/questions/355060/c-sharp-vs-java-generics

https://stackoverflow.com/questions/31693/what-are-the-differences-between-generics-in-c-sharp-and-java-and-templates-i

C# vs Java : Generics
http://toddgerspacher.blogspot.com/2017/07/c-vs-java-generics.html

Generics in Java
https://en.wikipedia.org/wiki/Generics_in_Java#Problems_with_type_erasure

Generics in the Run Time (C# Programming Guide)
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/generics/generics-in-the-run-time

.NET Column: Introducing Generics in the CLR
https://docs.microsoft.com/en-us/archive/msdn-magazine/2003/september/net-column-introducing-generics-in-the-clr
Finally, the research group at Microsoft has modified a version of the shared source common language implementation (CLI), code-named "Rotor," to include generics support.

https://dotnetfiddle.net/MEK7FM

checked 關鍵字

範例
https://dotnetfiddle.net/Ubmgeg

REF:
https://docs.microsoft.com/zh-tw/dotnet/csharp/language-reference/keywords/checked
https://dotblogs.com.tw/yc421206/2012/10/15/77489

reference types(參考型別)在哪種狀況下不同變數會被彼此影響?

微軟官網文件
『With reference types, it is possible for two variables to reference the same object and thus possible for operations on one variable to affect the object referenced by the other variable』
https://docs.microsoft.com/en-us/dotnet/csharp/tour-of-csharp/types-and-variables
做了一個比較
Java也有同樣的特性，Java叫做Primitive Type (基本型態)、Class Type / Reference Type (類別型態 / 參考型態)
但是Java沒有struct類型(型別)

使用reference types(變數會被彼此影響)
https://dotnetfiddle.net/zURcCT


使用value types(變數不會被彼此影響)
https://dotnetfiddle.net/nNaCPE 


自己整理的C#和Java比較
https://hackmd.io/SVIGNsLLRkqYxywgJpcgTg