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[Java教程]【持续更新】把.net代码转换为java代码的注意事项


国内大多数大学的软件相关专业大多强制学生学习c和Java,但.net 的几个语言可以说是选学的。

由于visual studio在windows平台上使用相对方便,一些同学会在上大学的Java课之前自学.net开发技术。

这一类同学就需要一些代码转换技巧来帮助学习Java。

在这之前我吐槽一下TinyMCE编辑器,它不能正确染色一些vb.net的关键字,比如Async, NameOf, Aggregate 。c#的某些关键字也不能正确染色,如__arglist。

由于我这学期才开始上Java课,代码中出现的错误欢迎大家指正。

1. 枚举类型

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    }

转换成Java是这样的。感觉跟c++/cli和c++/cx的enum class差不多。

如果原先的枚举比较长,最好写个小程序转换一下。

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);  }}

那个__value是我抄.net参考源码的,如果看不顺眼可以改名。

2.异常

Java的异常如果不是RuntimeException这一类的,就得用Throws 声明,否则像AccessViolationException这一类错误一样只能在UnhandledException(ErrorListener)那里处理。

转换代码的时候写一堆Throws比较麻烦,写了一层就忘了下面那一层有什么异常了。

这个比较好办,只要不是致命的异常,那自定义异常就都继承RuntimeException好了。自带的几个需要用Throws的异常用ErrorListener拦截。

class PointOutOfScreenException extends RuntimeException{  public PointOutOfScreenException(){    super("点出屏幕了...");  }}

 

3.标识符类型的推断

VB

Dim a = New StringBuilder

C#

var a = new StringBuilder();

转换成Java就用复制粘贴大法,把类名复制一下然后粘贴到开头

StringBuilder a = new StringBuilder();

4. c#不安全模式, vb和f#各种调运行库的独有运算符, 动态, async, await, linq, 无符号类型 .......

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: 自己重新写吧。直接转换这种代码反而浪费时间!


 

我还要上课呢,这次就写到这里吧。喜欢Java的可以找出描述不合理的地方,但是请勿喷。