Allow the user to run the program step by step

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Allow the user to run the program step by step

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#1 by (1 votes)

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Hello, I'm in the development part of my TCC that consists of a graphing support tool (more precisely some algorithms such as Traveling Clerk, Minimum Generating Tree, etc ...) and would like to allow the user to execute the program in step-by-step mode, so that the user can control the execution of the algorithms and have time to observe the changes.

I would like suggestions on how to implement the walkthrough feature, whether there is any standard, library, or if someone has already implemented something similar and could share the code for study.

java

asked by anonymous 08.01.2015 / 22:11

1 answer

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score 1 · Accepted Answer

There are two answers to what you want.

The simple answer is to prepare the environment for you to show how to run the algorithm step by step but not implement a fully functional code debugger. Somewhat like the one posted here on this page

The complicated answer is you enter the JVM debugger documentation site and try to understand how the debugger works. Or even see how some simple debbuger implementation was done but I believe that is not exactly what you are looking for.

I recommend that you use the first solution. Pre-prepare each of the screens for each type of algorithm you want to run with buttons for start and go to the next step. To run an algorithm step by step you need to deconstruct your loop and turn it into functions, for example:

Bubble sort:

public static void bubbleSort(int[] array) {
    for (int j = 1; j < array.length; j++) {
        for (int i = 0; i < array.length - j; i++) {
            if (array[i] > array[i + 1]) {
                int tmp = array[i + 1];
                array[i + 1] = array[i];
                array[i] = tmp;
            }
        }
    }
}

You first have to extract the inner part like this:

public static void bubbleSort(int i , int[] array) {
    if (array[i] > array[i + 1]) {
        int tmp = array[i + 1];
        array[i + 1] = array[i];
        array[i] = tmp;
    }
}

Now you need to put the correct inputs to this part by simulating execution. Here's a complete example to give you an idea:

import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

public class Sorter {

    public static void main(String[] args) {

        final int[] array = {5, 2, 4, 6, 1, 3};
        final List<Integer> contextValues = new ArrayList<Integer>();

        for (int j = 1; j < array.length; j++) {
            for (int i = 0; i < array.length - j; i++) {
                contextValues.add(i);
            }
        }
        System.out.print("Array:");
        printArray(array);
        System.out.println();
        //executa a cada 1 segundo um passo do bubble sort
        final Timer t = new Timer();
        t.scheduleAtFixedRate(new TimerTask() {
            int step = 0;

            @Override
            public void run() {
                System.out.println("--------------");
                System.out.println("Passo " + step);
                bubbleInPosition(array, contextValues.get(step));
                printArray(array);

                if (step > contextValues.size()) {
                    t.cancel();
                }
                step++;
            }
        }, 0, 1000);

    }

    public static void printArray(int array[]) {
        System.out.print("[");
        for (int i : array) {
            System.out.print(" " + i + " ,");
        }
        System.out.print("]");
    }

    private static void bubbleInPosition(int[] array, int i) {
        if (array[i] > array[i + 1]) {
            int tmp = array[i + 1];
            array[i + 1] = array[i];
            array[i] = tmp;
        }
    }
}

In place of the Timer you would have to call the next step button. This would be a simple idea, but it can be applied to various algorithms.