Continueouse Update in Java Continuous Update in Java
Most of the software related majors in most universities in China have learned C and Java, but several languages in .NET can be said to be choosch.
Since Visual Studio is relatively convenient on the Windows platform, some classmates will self-study .NET development technology before the Java class at the University.
This class of students require some code conversion skills to help learn Java.
Reprint, please indicate the author nukepayload2
Before this, I spitted Tinymce editor, it won't correctly dyed some keywords in VB.NET, such as Async, Nameof, Aggregate. Some keywords C # cannot be stained correctly, such as __ARGLIST.
Since I have begun to go to Java lessons, the misfortunes appearing in the code welcome everyone.
Enumeration type
VB
Public Enum Direction Right = 1 DownRight Down DownLeft Left UpLeft Up UpRight End Enum
C#
public enum Direction { Down = 1, DownLeft, Left, UpLeft, Up, UpRight, Right, DownRight }
Convert to Java is like this. It feels almost the same as C ++ / CLI and C ++ / CX.
If the original enumeration is longer, it is best to write a small program to switch.
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); } }
That __value is my copy .Net reference source, if you see it, you can change your name.
2. Abnormal
Java's exception is not RuntimeException, you have to use the throws declaration, otherwise you can only process the unhandledException (ERRORLISTENER) like AccessviolaionException.
When converting the code, write a bunch of throws. Trouble, write a layer, I forgot what is abnormal.
This is better, as long as it is not a fatal exception, the custom exception is inherited to RuntimeException. Several several need to use the exception to ErrorListener with error.
class PointOutOfScreenException extends RuntimeException{ public PointOutOfScreenException(){ super("Out of the screen ..."); } }
have to be aware of is
<1> Java does not support an abnormal filter.
<2> Java does not support Try ... catch ... fault in MSIL (Using in VB, Using in C #)
3. Inference of the identifier type
VB
Dim a = New StringBuilder
C#
var a = new StringBuilder();
Convert to Java and copy the Dafa with copy, copy the class name and paste it to the beginning.
StringBuilder a = new StringBuilder(); 4. C # unsafe mode, VB and F # Various operators, dynamics, async, await, linq, no symbol type, event, delegate, custom value type, generic constraint
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: Write yourself. Directly convert this code but waste time!
5. Event and commission
There is no article in this case, because Java has an anonymous class for the interface.
VB
Event Slide(sender As Object, e As SlideEventArgs)
C#
delegate void SlideEventHandler(object sender, SlideEventArgs e); event SlideEventHandler Slide;
Java
interface SlideEventHandler{ void slide(Object sender, SlideEventArgs e); }
VB processing event
Sub xx_Slide(sender As Object, e As SlideEventArgs) Handles xx.Slide ... End Sub
C # handling events
Class name () { xx.Slide += xx_Slide; } void xx_Slide(object sender, SlideEventArgs e) { ... }
VB uses lambda expression handling events
AddHandler xx.Slide, Sub(sender, e) ...
C # uses Lambda Expressions Processing Events
xx.Slide += (sender, e) => ... ;
Java processing event
xx.setSlideListener(new SlideEventHandler(){ void slide(Object sender, SlideEventArgs e){ ... } });
I haven't seen JDK 1.8 Lambda expressions can not be used to handle events and complete delegates, so they do not provide Java code in this area.
6. Important modifiers
Access level modifier
| VB | C# | Java |
| Private | private | private |
| Protected | protected | not support |
| Protected Friend | protected internal | protected |
| Friend | internal | This is the default value |
| Public | public | public |
Inheritance and polymorphic correlation modifiers
| VB | C# | Java |
| MustInherit | abstract | abstract |
| MustOverride | abstract | abstract |
| Overridable | virtual | This is the default value |
| Overrides | override | @override |
| Overloads | overload | This is the default value |
| Shadows | new | not support |
| NotOverridable | sealed | final |
Member class identifier
| VB | C# | Java |
| Class | class | class |
| Module | [StandardModule()] static sealed class | Final Class (inaccurate) |
| Event | event | not support |
| Custon Event | event | not support |
| Delegate | delegate | not support |
| Property | Omitted | not support |
| Dim | Omitted | Omitted |
| Interface | interface | interface |
| Function | Omitted | Omitted |
| Sub | Omitted | Omitted |
7. Parameter passed
The following is a comparison of parameters.
| VB | C# | Java |
| ByVal (This is the default value) | This is the default value | This is the default value |
| ByRef | ref | not support |
| ParamArray | params | ... |
| not support | __arglist | not support |
| not support | * (Direct finger) | not support |
| <In> | in | This is the default value |
| <Out> | out | not support |
8. Attribute
Java does not support attributes, so you must write a method to encapsulate private fields :(
VB
Public Property LastUpdateTimestamp As Date
C#
public DateTime LastUpdateTime { get; set;}
Java
private DateTime lastUpdateTime; public DateTime getLastUpdateTime(){ return lastUpdateTime; } public void setLastUpdateTime(DateTime value){ lastUpdateTime = value; }
Write here this time. Like Java, you can find an unreasonable place, but don't spray.
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Source: https://programmerall.com/article/51341360923/
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