Android : call class file from assets

i want to use class in assets

if i put project HelloWorld2 in helloWorld/assets

could i call MainActivity2(helloworld/assets/HelloWorld2/MainActivity2) from MainActivity(helloWorld/src)?

i can read MainActivity2.java in assets but can't execute MainActivity2.java from MainActivity.... :(

=== MainActivity

        AssetManager assetManager=getAssets();
        InputStream inputStream=null;
        try {
            inputStream=assetManager.open("HelloWorld2/src/com/example/helloworld2/MainActivity2.java");                        
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        String s= readTextFile(inputStream);
        Toast.makeText(getApplicationContext(),"readTextfile : "+ s, Toast.LENGTH_LONG).show();
    }
}

private String readTextFile(InputStream inputStream){
    ByteArrayOutputStream outputStream=new ByteArrayOutputStream();
    byte buf[]=new byte[1024];
    int len;

    try{
        while((len=inputStream.read(buf))!=-1){
            outputStream.write(buf,0,len);
        }

    outputStream.close();
    inputStream.close();
    }
    catch(IOException e){

    }
    return outputStream.toString();
}