【持續更新】把.net代碼轉換為java代碼的注意事項，.netjava

【持續更新】把.net代碼轉換為java代碼的注意事項，.netjava

國內大多數大學的軟體相關專業大多強制學生學習c和Java，但.net 的幾個語言可以說是選學的。

由於visual studio在windows平台上使用相對方便，一些同學會在上大學的Java課之前自學.net開發技術。

這一類同學就需要一些代碼轉換技巧來協助學習Java。

在這之前我吐槽一下TinyMCE編輯器，它不能正確染色一些vb.net的關鍵字，比如Async, NameOf, Aggregate 。c#的某些關鍵字也不能正確染色，如__arglist。

由於我這學期才開始上Java課，代碼中出現的錯誤歡迎大家指正。

1. 枚舉類型

VB

Public Enum Direction    Right = 1    DownRight    Down    DownLeft    Left    UpLeft    Up    UpRightEnd Enum

C#

        public enum Direction        {            Down = 1,            DownLeft,            Left,            UpLeft,            Up,            UpRight,            Right,            DownRight        }

轉換成Java是這樣的。感覺跟c++/cli和c++/cx的enum class差不多。

如果原先的枚舉比較長，最好寫個小程式轉換一下。

public enum Direction {            Down(1),            DownLeft(2),            Left(3),            UpLeft(4),            Up(5),            UpRight(6),            Right(7),            DownRight(8)    private int __value;    private Direction(int value) {        this.__value = value;    }    @Override    public String toString() {        return String.valueOf(this.nCode);    }}

那個__value是我抄.net參考源碼的，如果看不順眼可以改名。

2.異常

Java的異常如果不是RuntimeException這一類的，就得用Throws 聲明，否則像AccessViolationException這一類錯誤一樣只能在UnhandledException（ErrorListener）那裡處理。

轉碼的時候寫一堆Throws比較麻煩，寫了一層就忘了下面那一層有什麼異常了。

這個比較好辦，只要不是致命的異常，那自訂異常就都繼承RuntimeException好了。內建的幾個需要用Throws的異常用ErrorListener攔截。

class PointOutOfScreenException extends RuntimeException{    public PointOutOfScreenException(){        super("點出螢幕了...");    }}

 

3.標識符類型的推斷

VB

Dim a = New StringBuilder

C#

var a = new StringBuilder();

轉換成Java就用複製粘貼大法，把類名複製一下然後粘貼到開頭

StringBuilder a = new StringBuilder();

4. c#不安全模式, vb和f#各種調運行庫的專屬運算子, 動態, async, await, linq, 無符號類型 .......

VB

        Async Function LoadImages(device As CanvasDevice) As Task            forestTiles = Await SpriteSheet.LoadAsync(device, $"SpriteSheets/ForestTiles{NameOf(ImageID)}.png", New Vector2(64, 64), Vector2.Zero)            wizardWalk = Await SpriteSheet.LoadAsync(device, "SpriteSheets/WizardWalkRight.png", New Vector2(128, 192), New Vector2(64, 150))            wizardIdle = Await SpriteSheet.LoadAsync(device, "SpriteSheets/WizardIdleRight.png", New Vector2(128, 192), New Vector2(64, 150))        End Function

C#

        async Task LoadImages(CanvasDevice device)        {            forestTiles = await SpriteSheet.LoadAsync(device, $"SpriteSheets/ForestTiles{nameof(ImageID)}.png", new Vector2(64, 64), Vector2.Zero);            wizardWalk = await SpriteSheet.LoadAsync(device, "SpriteSheets/WizardWalkRight.png", new Vector2(128, 192), new Vector2(64, 150));            wizardIdle = await SpriteSheet.LoadAsync(device, "SpriteSheets/WizardIdleRight.png", new Vector2(128, 192), new Vector2(64, 150));        }

VB

    Public Function CalculateClipGeometry(resource As ICanvasResourceCreator, SourcePoint As Vector2, Geometies As CanvasGeometry(), ScreenSize As Size) As CanvasGeometry        Dim geos = Aggregate geo In Geometies                       Let Lines = Aggregate tes In geo.Tessellate                                   From ln In {New LineSegment(tes.Vertex1, tes.Vertex2), New LineSegment(tes.Vertex1, tes.Vertex3), New LineSegment(tes.Vertex3, tes.Vertex2)}                                   Select ln Distinct Into ToArray                       Select Rays = Aggregate tes In geo.Tessellate                           From light In {New LineSegment(SourcePoint, tes.Vertex1), New LineSegment(SourcePoint, tes.Vertex2), New LineSegment(SourcePoint, tes.Vertex3)}                               Where Not (Aggregate l In Lines Where light.RayToBoundary(ScreenSize).HasIntersection(l) Into Any)                           Select light                       Into ToArray                       Where Rays.Length >= 2 AndAlso Rays(0).Name Like "Ln*"                       Let Fir = Rays.First                       Select Arr = Aggregate ln In Rays Order By ln.Angle(Fir) Into ToArray                       Select CanvasGeometry.CreatePolygon(resource, {Arr.First.Point2, Arr.First.RayToBoundary(ScreenSize).Point2, Arr.Last.RayToBoundary(ScreenSize).Point2, Arr.Last.Point2})                   Into ToArray        Return geos.Union    End Function

C#

 public unsafe void AddThree(__arglist) {    var args = new ArgIterator(__arglist);    var a = (byte*)TypedReference.ToObject(args.GetNextArg());    *a+=3; }

 

Java

// TODO: 自己重新寫吧。直接轉換這種代碼反而浪費時間！

 

我還要上課呢，這次就寫到這裡吧。喜歡Java的可以找出描述不合理的地方，但是請勿噴。