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I am a total newbie when it comes to coding. I have been plugging away at getting my mind around Java for about a week.

Background

I have been sick for a while with symptoms that resemble some form of chronic fatigue, and my doctor handed me a flow chart that tells me how much activity I should do before taking an equal sized break, based on how I feel.

One look at the flow chart and I realized that she could have just as well handed me a flowchart of a program heh. So I decided to make my first little program in Java.

The code its self was done in a couple of hours (I am a bit of a newbie, remember), but for about a week now, I have spent time learning and improving it when I learn something new and relevant to the project.

My goal here:

I want to learn to code and follow conventions correctly. So I dare not write another program without peer review first, in case I'm doing things wrong or inefficient. I would appreciate any and all comments that can help me improve or encourage me.

Disclaimer stuff:

  • The time in minutes is shown as x simply because that's how it was on the flow chart. Though no, "x" isn't super 'readable'. :)
  • The last StringBuilder at the bottom should probably be turned into a System.out.printf so that I can control those decimal points (I just ran the program and input 32 minutes and seen all those digits for the first time when the build was finished.. heh).

Other than that, I hope you can dissect this thing and offer some good corrections or alternative methods so I can start coding again! :)

package activity;

import java.util.Scanner;

// @author Jack

public class Activity {

    //x; = time in minutes.
    static int x;

    //Flag to stop the loop which encloses the following indented.
    static boolean timeInMinutesGiven = false;
        static boolean validReply = false;
        static String timeRealisticIs;
        static boolean userAcceptsRejectsInput = false;

    static String dayIs;
    static boolean goodBadChoiceFlag = false;
    //activityTimeModifier; = used in the calculation of stepUpTime.
    static double activityTimeModifier;
    //int stepUpTime; = the final time output.
    static double stepUpTime;
    static double subtractedByX;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        /*
        The while/do while loops handle prompting and information gathering
        */

        while (!timeInMinutesGiven) {

        //This loop prompts user to give a value for 'x', time in minutes.
            do {
                System.out.print("How long (in minutes) can you be active "
                        + "today before symptoms start to appear?: ");

                try {
                    Scanner input = new Scanner(System.in);
                    x = input.nextInt();
                    validReply = true; //If user gave an integer.
                } catch (Exception e) {
                    System.out.println("ERROR: A whole number was expected.");
                    validReply = false; //If user gave !integer.
                }

            } while (!validReply);

            //This loop prompts user for 'Are you sure?'.
            do{
                StringBuilder areYouSure = new StringBuilder();
                areYouSure.append("Can you REALLY be active for ")
                          .append(x)
                          .append(" minutes at a time?: ");
                System.out.print(areYouSure.toString());
                Scanner yesNoInput = new Scanner(System.in);
                timeRealisticIs = yesNoInput.nextLine();

                //if and else if would both trigger this anyway.
                userAcceptsRejectsInput = true;

                if (timeRealisticIs.equalsIgnoreCase("yes")
                        || timeRealisticIs.equalsIgnoreCase("y")) {
                    timeInMinutesGiven = true;

                } else if (timeRealisticIs.equalsIgnoreCase("no")
                        || timeRealisticIs.equalsIgnoreCase("n")) {
                    System.out.println("Sequence Restarted:");

                } else {
                    System.out.println("Error: One of the following "
                            + "must be entered:");
                    System.out.println("Yes, y, no, n");
                    System.out.println("Asking again:");
                    userAcceptsRejectsInput = false;

                }
            }while (userAcceptsRejectsInput == false);
        }

        System.out.println(x + " minutes accepted.");

        //Asks user if dayIs good or bad. 
        //The result sets the activityTimeModifier variable.
        do {
            System.out.println("Is this a good or bad day?");
            System.out.print("(Expected: Good/Bad): ");

            Scanner inputDay = new Scanner(System.in);
            dayIs = inputDay.nextLine();

            /*
            The if statements handle the results of the
            information gathered during the while loops
            */
            if (dayIs.equalsIgnoreCase("good")
                    || dayIs.equalsIgnoreCase("g")) {
                System.out.println("A good day!! How wonderful!");
                System.out.print("Since you are feeling so good, ");
                activityTimeModifier = 0.2;
                goodBadChoiceFlag = true;

            } else if (dayIs.equalsIgnoreCase("bad")
                    || dayIs.equalsIgnoreCase("b")) {
                activityTimeModifier = 0;
                goodBadChoiceFlag = true;
                System.out.print("Thats alright, then ");

            } else {
                StringBuilder goodBadExpected = new StringBuilder();
                goodBadExpected.append("Error: 'Good' or 'bad' expected.\n")
                        .append("You typed: '").append(dayIs).append("'\n")
                        .append("Asking again:");
                System.out.println(goodBadExpected.toString());
            }
        } while (!goodBadChoiceFlag);

        /*
        The following code runs the final calculation of the result 
        of the 'while' input gathering and the result of the 
        'if' input and variable initialization.
        */
        stepUpTime = x + activityTimeModifier * x;
        subtractedByX = stepUpTime - x;
        StringBuilder balancedTimeString = new StringBuilder();
        balancedTimeString.append("your balanced training time ")
                          .append("for today will be set to: ")
                          .append(stepUpTime)
                          .append(" minutes.\n")
                          .append("That is ")
                          .append(subtractedByX)
                          .append(" minutes longer than ")
                          .append(x)
                          .append(".");
        System.out.println(balancedTimeString.toString());
    }
}
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Documentation

Documentation is overestimated. The only truth lies in the executable parts of your source code. The way code emerges the same way documention has to emerge and that is an experienced problem. Often these elements diverge when development goes on so documentation begins to lie about the things happening in the executable parts so it confuses more than it helps. Documentation often becomes an alibi for bad code.

My suggestion is as soon as you are dealing with interfaces you should learn how to write JavaDoc for central interfaces that define the development responsibility borders or system borders. So source code should consequently be documented at those borders.

Sometimes it is necessary to give an inline hint what is the intention. But most of the time your code should express exactly the requirement so no further documentation is neccessary.

But why I am talking so much? It is because you should not create comments like "This loop prompts user to give a value for 'x', time in minutes" if the following loop prompts user to give a value for 'x', time in minutes.

Naming

We have several mechanisms to make complex things more ascertainable without falling into a delusion of documentation. One very important thing is "Naming".

From some occuring names you are not able to evaluate a meaning. If you translate "x" for the user during output to "time In minutes" why not simply name the variable "timeInMinutes".

Another problem is the abstraction level of names. Often abstraction levels are mixed. That relates to control flow and names as well. Your "validReply" can be evaluate to a lot of meanings as reply is not very concrete. But you are handling a concrete case: a (maybe very optimistic) validation if a "time in minutes" was successfully entered: "hasGotValidTimeInMinutes" for example would be a variable name of the current abstraction level.

Modularization

To make a developers life easier you should not flood your brain with information. Keep your stack "small". Your main-method is NOT small. Asking for "timeInMinutes" is one part. Asking for "Are you sure?" another. Those things can be viewed separately with "timeInMinutes" as the only connection to "Are you sure?"

Modularization can take place variously. In your case I would start to "extract" a method. This is a typical IDE supported operation but you also can do it by hand. You should watch a video on youtube how to do this for the IDE you use. For your "timeInMinutes"-loop where you get the time in minutes you should mark the whole loop and perform an "extract method" refactoring operation either with the help of the IDE or by hand. The name of the new method should be something like "getTimeInMinutes".

You should slice the main-method into several other methods each method doing on well-defined thing. What we are doing here is applying the so called single responsibility principle (SRP) in a very basic way. The main task in SRP is to achieve a 1 to 1 relationship from a code fragment to a responsibility. Things that belong together should be together. Things that do not belong together should be separated.

You should continue to extract methods and separate the responsibilities.

Method local variables

Currently you are using the variable "validReply" only within the new method "getTimeInMinutes". So why removing it from the global scope and declaring it locally in the method.

Why should we do that? Currently you know that the variable "validReply" is only used by this code fragment. But other developers hav to evaluate that Their mind have to process much more information to identify this relationship between the variable and the algorithm. Their mind has to hide other global variables and consider them as not relevant.

In those small scenarios it is less a problem. But in professional software development with thousands of classes maximal neccessary scope of ANYTHING is the Holy Grail. So put your variables in the scope they are needed but keep them as hidden as possible.

The "validReply" variable should be declared within the new extracted method.

Encapsulation

Here we mean that things have an inner state and an outer state and the inner state is totally hidden to us and our efforts to directly modify it.

If we take the new extracted method as an example. It is currently not well encapsulated. The variable "x" or now "timeInMinutes" can be easily modifed by other algorithms which is called "side effect".

We should introduce a variable with the same name (timeInMinutes) in the new method "getTimeInMinutes". Furthermore we will introduce a return value and assign the returned value to the gobal scope variable "timeInMinutes". We now successfully improved the encapsulation of the method. It is not perfect but it will do the job.

Now I want to show the final result of our refactorings:

public class Activity {

    ...

    static int timeInMinutes;

    ...

    public static void main(String[] args) {

        ...

        while (!timeInMinutesGiven) {

            ...

            timeInMinutes = getTimeInMinutes();

            ...

        }

        ...

    }

    private static int getTimeInMinutes() {

        int timeInMinutes = 0;
        boolean hasGotValidTimeInMinutes;

        do {

            System.out.print("How long (in minutes) can you be active " + "today before symptoms start to appear?: ");

            try {
                Scanner input = new Scanner(System.in);
                timeInMinutes = input.nextInt();
                hasGotValidTimeInMinutes = true;
            } catch (Exception e) {
                System.out.println("ERROR: A whole number was expected.");
                hasGotValidTimeInMinutes = false;
            }

        } while (!hasGotValidTimeInMinutes);

        return timeInMinutes;
    }

}

Further studies

If you want to learn to program you have to manage following things:

  1. Learn the theory of sequence, selection and iteration

  2. Train your algorithmic thinking by solving problems with the elements of 1. in a programming language of your choice by increasing difficulty

  3. Get familiar with the language mechanisms

  4. Apply programming paradigms like functional or object-oriented programming

  5. Formalize you code fragments by learning the currently identified 26 design patterns and learn to to apply them in the correct situations

  6. Organize your code by following the correct semantic of each code fragment and learn and apply the SOLID principles as they guide you through the jungle of design decisions

  7. Learn the restrictions of the language you use for a problem. Maybe in another language you are able to express the solution in another way that is more elegant.

I think that you defintely managed 1. and 2. but your current focus should lie on 3.

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  • 1
    \$\begingroup\$ For anyone who found oopexpert's amazing advice to be as relevant and helpful as I have, you might want to take a look at this video series about Refactoring: youtube.com/watch?v=vhYK3pDUijk (video 2 in the series shows you how to manually extract code to functions but the whole series looks helpful). \$\endgroup\$ – Jack Suede Feb 17 '17 at 12:25

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