Java to C# Converter

Java to C# converter. Uses JavaParser to parse the Java source code text, IKVM.NET to convert the javaparser .jar into a .NET .dll, and Roslyn for C# AST generation.

Pull requests and issue submission welcome.

Getting Started

Clone the repo, build, and launch the Gui WPF app. Click the "..." button on the left side to load a Java file, and then click Convert to convert to C# on the right side. Please note that conversion may take up to a few minutes on large files.

Alternatively, launch the command line (Cli) version to process files from the command line.

The core library is installable via NuGet at https://www.nuget.org/packages/JavaToCSharp/

Syntax Mappings

By default, JavaToCSharp translates some usual Java classes and methods into their C# counterparts (e.g. Java maps are converted into dictionaries). You can specify additional mappings to fine tune the translation of the syntactic elements.

The mappings are specified in a yaml file with root keys that represent the kind of mapping, each having a set of key-value pairs that specify the java to C# mappings:

• ImportMappings: Mappings from Java package names to the C# namespaces. If a key-value pair has an empty value, the package will be removed from the resulting C#.
• VoidMethodMappings: Mappings from unqualified Java void methods to C#.
• NonVoidMethodMappings: Same as before, but for non-void java methods.
• AnnotationMappings: Mappings from Java method annotations to C#.

For example, to convert JUnit tests into xUnit you can create this mapping file:

ImportMappings:
  org.junit.Test : Xunit
  org.junit.Assert.assertEquals : ""
  org.junit.Assert.assertTrue : ""
VoidMethodMappings:
  assertEquals : Assert.Equal
  assertTrue : Assert.True
AnnotationMappings:
  Test : Fact

If you specify this file in the --mappings-file CLI argument, the conversion of this JUnit test:

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class MappingsTest {
  @Test
  public void testAsserts() {
    assertEquals("a", "a");
    assertTrue(true);
  }
}

will produce this xUnit test:

using Xunit;

public class MappingsTest
{
  [Fact]
  public virtual void TestAsserts()
  {
    Assert.Equal("a", "a");
    Assert.True(true);
  }
}

.NET Support

Trunk will generally always target the latest LTS version of .NET for the core library and the CLI/GUI apps. If you require running the app on a prior version of .NET, please see the historical releases. Where STS BCL or preview (as of latest LTS SDK) C# language features are used in the converter, they will be options that are disabled by default. These options may become enabled by default when the next LTS ships, as a major version bump.

.NET Framework is no longer supported and will not be supported going forward. This includes not just for the core library (i.e. .NET Standard will not be supported) and running the CLI/GUI apps, but also for the C# code generation where applicable. You should be running .NET LTS nowadays anyways (.NET 6+ at the time of writing).

Bug fixes and features may be backported to the latest major version that targets an actively-supported, non-latest .NET LTS, but only based on community interest. Please submit an issue if you want a bugfix or feature backported; better yet, please submit a PR. Only clean cherry-picks or minor merges will be supported for backports; significant/messy merges or PRs will likely not be supported or merged.

License for JavaParser

Licensed under the Apache License available at https://github.com/javaparser/javaparser/blob/master/LICENSE.APACHE