• The Idea:
  • In many aspects of life, both personal and professional, it is necessary to determine if criteria have been satisfied
  • One common way to do this is to use a checklist
• An Example:
  • A personal packing list for a trip

• Representing the Criteria:
  • A String[] (named checklist) is very flexible
• Representing the Accomplishments:
  • A conformal boolean[] assumes that everything accomplished is on the checklist
  • A String[] (named completed) is more flexible

javaexamples/programmingpatterns/checklist/Fragments.java (Fragment: 0)

        boolean done  = false;        
        for (int a = 0; a < accomplished.length; a++) {
            if (accomplished[a].equals(checklist[index])) {
                done = true;
                break;
            }
        }
        

• What We Have:
  • done will contain true if and only if checklist[index] has been completed
• What We Need:
  • To nest this loop inside of another loop
• How?
  • There are many ways to do this incorrectly

javaexamples/programmingpatterns/checklist/Inflexible.java (Fragment: 0)

    /**
     * An n out of n checklist.
     *
     * @param checklist  The checklist
     * @param accomplished  The array of accomplished items
     * @return true if the Checklist is satisfied; false otherwise
     */
    private static boolean checkFor(String[] checklist, String[] accomplished) {
        boolean checked;
        for (int c = 0; c < checklist.length; c++) {
            checked = false;

            for (int a = 0; a < accomplished.length; a++) {
                if (checklist[c].equals(accomplished[a])) {
                    checked = true;
                    break;
                }
            }            
            if (!checked) return false; // An item was not accomplished
        }
        return true; // All items were accomplished
    }
        

javaexamples/programmingpatterns/checklist/Elegant.java (Fragment: outerChecklist)

    /**
     * An m (required) out of n (size) checklist.
     *
     * @param checklist  The checklist
     * @param accomplished  The array of accomplished items
     * @param needed     The required number of checklist items
     * @return true if the checklist is satisfied; false otherwise
     */
    private static boolean checkFor(String[] checklist, String[] accomplished, 
                                    int needed) {
        int       count;        
        count = 0;
        for (int c = 0; c < checklist.length; c++) {
            for (int a = 0; a < accomplished.length; a++) {
                if (checklist[c].equals(accomplished[a])) {
                    count++;
                    
                    if (count >= needed) return true;
                    else                 break;
                }
            }
        }
        return false; // Not enough items were accomplished
    }
        

• checklist:
  • "Shirts", "Socks", "Pants", "Skirts"
• completed for the Inflexible Variant:
  • "Shirts", "Socks", "Pants", "Dresses", "Shoes"
  • "Socks", "Shirts", "Skirts", "Pants"
• completed for the Flexible Variant when needed is 2):
  • "Shirts", "Socks", "Pants", "Dresses", "Shoes"
  • "Dresses", "Shirts"