/**
Driver class for inner class example, from recitation 5 Jan 2001
*/
class Outer {
	private int sum;
	/* note: having this variable out here with class scope is
	not a particularly good design decision.
	*/

	/**
	Implementation of a file summer with a named inner class
	*/
	int sumFileV1 (String fileName) {
		sum = 0;
		ProcessFile (fileName, new addLine ());
		return sum;
	} // end sumFileV1

	/**
	Implementation of a file summer with an anonymous inner class
	*/
	int sumFileV2 (String fileName) {
		sum = 0;
		ProcessFile (fileName, new LineProcessor() {
			public void doIt (String line)
			{
				sum += Integer.parseInt(line);
			}
		 }
		);
		return sum;
	} // end sumFileV2

	/**
	Implementation of a file summer that doesn't use an outer class variable
	*/
	int sumFileV3 (String fileName) {
		LPReturningInt lp;
		// We need to instantiate this into a variable so we
		// can call it at the end to return its answer
		lp = new LPReturningInt () {
			private int mySum = 0;
			public void doIt (String line)
			{
				mySum += Integer.parseInt(line);
			}
			public int getAnswer ()
			{
				return mySum;
			}
		};
		ProcessFile (fileName, lp);
		return lp.getAnswer();
	} // end sumFileV3

	/**
	Named inner class to add line's value to outer class property
	*/
	private class addLine implements LineProcessor {
		public void doIt (String line)
		{
			sum += Integer.parseInt(line); // .IntegerValue();
			/* The example in class erroneously tried to
			   call IntegerValue here.  But it turns out
			   that parseInt returns an int, not an Integer.
			*/
		}
	}

	/**
	Driver method for callbacks
	*/
	void ProcessFile (String fileName, LineProcessor lp)
	{
		String line;
		while ((line = MagicallyGetLine (fileName)) != null)
			lp.doIt (line);
	}
	/**
	Dummy so we can compile
	*/
	String MagicallyGetLine (String fileName)
	{
		return null;
	}
}

interface LineProcessor {
	public void doIt (String line);
}

interface LPReturningInt extends LineProcessor {
	public int getAnswer ();
}