The object is created in runtime or compile time

That's a complicated one, because strings are a special case: Interning of String in Java - GeeksforGeeks[^]

But for all other reference types, the answer is "run time only" - the compiler does not execute your code, so no object instances are actually created.
For example, if your class constructor always creates a file on disk, the file will not exist until your app has been compiled successfully, executed, and the code creates an instance of that class.