The program would fail to compile and the compiler would give you an error, saying that there is an "undefined symbol", "undefined variable", or some other error related to the Random class not being imported into your program.
However, you could still use methods and attributes from the "Random" class, without importing it, by using the fully qualified name of the class in any statements or lines of code that you write within your program.
For example, you could use the "Scanner" class without importing it by writing some code similar to the code below.
java.util.Scanner scan = new Scanner(System.in);
By using the above technique, you would be able to compile and run the program, but for every instance of the "Scanner" class that you'd like to use, you would have to create a new object using the fully qualified name of the "Scanner" (or any other) class.
Good luck and I hope I helped you!