Java from .NET and .NET from Java

Java or .NET? Why not both (when it is the only viable path)?

jni4net is a proven interop library for Java and .NET. Two brief examples developed by jni4net below merely require that you to specify the jni4net dependency in the (Visual Studio or Eclipse) project.

Calling Java from .NET

 using java.io;  
 using java.lang;  
 using java.util;  
 using net.sf.jni4net;  
 using net.sf.jni4net.adaptors;  
 namespace helloWorldFromCLR  
 {  
   public class Program  
   {  
     private static void Main()  
     {  
       // create bridge, with default setup  
       // it will lookup jni4net.j.jar next to jni4net.n.dll  
       Bridge.CreateJVM(new BridgeSetup(){Verbose=true});  
       // here you go!  
       java.lang.System.@out.println("Hello Java world!");  
       // OK, simple hello is boring, let's play with Java properties  
       // they are Hashtable realy  
       Properties javaSystemProperties = java.lang.System.getProperties();  
       // let's enumerate all keys.   
       // We use Adapt helper to convert enumeration from java o .NET  
       foreach (java.lang.String key in Adapt.Enumeration(javaSystemProperties.keys()))  
       {  
         java.lang.System.@out.print(key);  
         // this is automatic conversion of CLR string to java.lang.String  
         java.lang.System.@out.print(" : ");  
         // we use the hashtable  
         Object value = javaSystemProperties.get(key);  
         // and this is CLR ToString() redirected to Java toString() method  
         string valueToString = value.ToString();  
         java.lang.System.@out.println(valueToString);  
       }  
       // Java output is really Stream  
       PrintStream stream = java.lang.System.@out;  
       // it implements java.io.Flushable interface  
       Flushable flushable = stream;  
       flushable.flush();  
     }  
   }  
 }  

Calling .NET from Java

 import net.sf.jni4net.Bridge;  
 import java.io.IOException;  
 import java.lang.String;  
 import system.*;  
 import system.Object;  
 import system.io.TextWriter;  
 import system.collections.IDictionary;  
 import system.collections.IEnumerator;  

 public class Program {  
      public static void main(String[] args) throws IOException {  
           // create bridge, with default setup  
           // it will lookup jni4net.n.dll next to jni4net.j.jar   
           Bridge.setVerbose(true);  
           Bridge.init();  
           // here you go!  
           Console.WriteLine("Hello .NET world!\n");  
           // OK, simple hello is boring, let's play with System.Environment  
           // they are Hashtable realy  
           final IDictionary variables = system.Environment.GetEnvironmentVariables();  
           // let's enumerate all keys  
           final IEnumerator keys = variables.getKeys().GetEnumerator();  
           while (keys.MoveNext()) {  
                // there hash table is not generic and returns system.Object  
                // but we know is should be system.String, so we could cast  
                final system.String key = (system.String) keys.getCurrent();  
                Console.Write(key);  
                // this is automatic conversion of JVM string to system.String  
                Console.Write(" : ");  
                // we use the hashtable  
                Object value = variables.getItem(key);  
                // and this is JVM toString() redirected to CLR ToString() method  
                String valueToString = value.toString();  
                Console.WriteLine(valueToString);  
           }  
           // Console output is really TextWriter on stream  
           final TextWriter writer = Console.getOut();  
           writer.Flush();  
      }  
 }  

(verbose commenting by Pavel Savara, a jni4net contributor)

References:

http://zamboch.blogspot.com/2009/10/how-calling-from-net-to-java-works.html

http://zamboch.blogspot.com/2009/11/how-calling-from-java-to-net-works-in.html

https://github.com/jni4net/jni4net/tree/master/content/samples