Checking if file is in folder AND want to create a instance of that file if it exists

Question

So what I am trying to do is

Take user input (that is supposed to be a file name) and check if that file exists in my current work folder. ( I DONT NEED HELP HERE, this is under control)
If the file exists, I want to create an instance of that file. (I wanna do this so I can use reflections and check if the file is a particular interface, and check the constructor.

So for testing my program, i created an instance of a existing file like this:

File tempFile = new File("/CURRENTFOLDER/" + file + ".java");
//with the user input tempFile = Test1.


    if(tempFile.exists()){

        Test1 test1 = new Test1();
        Class<?> test1_class = test1.getClass();

but what i really wanna do is something like this:

   File tempFile = new File("CURRENTFOLDER" + file + ".java");

    if(tempFile.exists()){

        //Test1 test1 = new Test1();
        //Class<?> test1_class = test1.getClass();

        tempFile instance_of_tempFile = new tempFile();
        Class<?> ? test_class = instance_of_tempFile.getClass();

I know you can't write tempFile instance_of_tempFile = new tempFile();, but just included that so you understand what I'm trying to do.

There's no such thing as "creating an instance of a file". You seem to be mixing the concept of a file (something which lives outside Java) and a Class (something which lives inside). Please rewrite the question to clarify what (2) really means — drekbour
– drekbour, Commented Nov 8, 2019 at 10:16
You cannot create an instance of a class that only exists as source code in a .java file. It needs to be compiled to a .class file and be present in the classpath so you can use it using Class.byName. — f1sh
– f1sh, Commented Nov 8, 2019 at 10:23

Yuriy Tsarkov · Accepted Answer · 2019-11-08 10:32:52Z

1

Actually it's possible by using ClassLoader's

Basically you have to implement a Class Loader with a functionality that you need an then you will be able to instantiate a class by the file.

Here is a brief how-to

This example also can be useful

answered Nov 8, 2019 at 10:32

Yuriy Tsarkov

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1 Comment

Jappe Over a year ago

Thanks gonna check that out!!

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