Java Class Use Example

This is a basic example where we call a Java class from a .NET (6/7/Framework) application. This example consider:

• An installed JDK to build the Java snippet
• A development environment to build .NET project
• In runtime, the JRE/JDK location is identified using the standard methods: environment variable or Registry in Windows

Let’s consider a Java code like the following one:

public class JavaClass {
    /**
     * This simple method return the "Hello World!!" string
     * * @return "Hello World!!" string
     */
    public String helloWorld()
    {
        return "Hello World from Java!!";
    }

    /**
     * This simple method return the sum of two double
     * @param a
     * @param b
     * @return a + b
     */
    public double add(double a, double b)
    {
        return a+b;
    }

    /**
     * This simple method return the sin of a double
     * @param a
     * @return sin of a
     */
    public double sin(double a)
    {
        return Math.sin(a);
    }
}

Create a folder and save the above code in a file named JavaClass.java; compiles the file with a command like:

javac JavaClass.java

Write a .NET C# application like the following one:

using MASES.JCBridge.C2JBridge;
using System;

namespace JavaClassUseExample
{
    class TestClass : SetupJVMWrapper<TestClass>
    {
        public override string ClassPath { get { return @".\"; } }

        public void Execute()
        {
            var jCInstance = DynJVM.JavaClass.@new();
            double a = 2;
            double b = 3;
            double c = Math.PI / 2;
            string hello = jCInstance.helloWorld();
            double result = jCInstance.add(a, b);
            double sin = jCInstance.sin(c);
            Console.WriteLine("{0} {1} + {2} = {3} and sin({4:0.0000000}) = {5:0.00000000}", hello, a, b, result, c, sin);
            Console.WriteLine("Press Enter to exit");
            Console.ReadLine();
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                new TestClass().Execute();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                Console.WriteLine("Press any key.");
                Console.ReadKey();
            }
        }
    }
}

In the same folder where Java file was saved, create a .NET project and save the above code in a file named Program.cs; then compile the project with the preferred development tool.

Executing the C# code the developer has the following output:

Hello World from Java!! 2 + 3 = 5 and sin(3,1415927) = 1,00000000