/*
 * T05n01.java -- Using IFs to test pre- and post-conditions.
 *
 * Assertions have been added to Java for the purpose of giving Java
 * programmers a slightly nicer way to check for internal logic
 * errors that require program termination.  This program demonstrates
 * the traditional way of handling such problems, using IF statements
 * and manually terminating the program. 
 *
 * See T05n02.java for the same program with assertions.
 *
 * Note for IDE (Eclipse, Netbeans, TextPad, etc.) users:  This program
 * gets input from the command line.  This works great if you're running
 * the program from a terminal window, but when running from within an
 * IDE you'll need to figure out how to get your IDE to accept command
 * line arguments.  Consult your IDE's documentation.
 */

import java.io.*;

public class T05n01
{

        /* Find the smallest power of two greater than the 
         * given positive integer ceiling.
         * This version does the testing the old fashioned way,
         * without all that fancy assertion stuff.
         *   Pre-condition:   limit > 0
         *   Post-condition:  returns smallest power of two > limit
         */

    static int smallestPowerOf2 (int limit)
    {
        int product = 1;

        if (limit <= 0) {
            System.err.println("Pre-condition Error:  In smallestPowerOf2, "
                             + "limit must be > 0!");
            System.exit(1);
        }

        for (; product <= limit; product *= 2);  // good programming style?

        if (product/2 > limit) {
            System.err.println("Post-condition Error:  In smallestPowerOf2, "
                             + product + "is NOT is smallest "
                             + "power of 2 greater than " + limit + ".");
            System.exit(1);
        }

        return product;
    }


    public static void main (String [] args) 
    {
        int limit,
            powerOf2;

        if (args.length < 1) {
            System.out.println("\nUsage:  Provide a positive integer on the"
                             + " command line, and I'll find\nthe first"
                             + " power of 2 that exceeds it.\n\n");
            System.exit(1);
        }

        limit = Integer.parseInt(args[0]);

        powerOf2 = smallestPowerOf2(limit);

        System.out.println("smallestPowerOf2 says that the smallest power of 2 "
                         + "greater than " + limit + " is " + powerOf2 + ".");
    }
}