New to Java

I'm writing a program and would like to supply the user with the option to use their own values or use the default values of the program. I'd like to have it set up so the user can just hit enter in response to a question and use default values. I'm having trouble figuring out how to test for null/no/blank? input though. This is what I've got so far.

System.out.println("Please enter 4 superincreasing numbers separated by a comma and a space");
		System.out.println("Example: 1, 2, 4, 8");
		input = stdIn.nextLine();

		System.out.println("Input is:\""+ input +"\"");
		if (input == "" || input == null) //need help with this line
			System.out.println("No input");
		else
			System.out.println("Some input");

Unfortunately for me, I'm getting some input every time. What value do I need to test input against to see if nothing was entered?