CodeGym/Pomoc z zadaniami Java/'pl.codegym.task.task13.task1328.Solution.this' cannot be...

Poziom 20

Debica

28.09.2021
505widoki
9komentarze

'pl.codegym.task.task13.task1328.Solution.this' cannot be referenced from a static context: 9 and 10

Pytania dotyczące zadania

Walki robotów

Podstawy Java, Poziom 3, Lekcja 11

Rozwiązane

Hello, how to fix errors in these lines? They broke my validation.

1. Zapoznaj się z kodem.
2. Zaakceptuj swój los i postaraj się zrozumieć kod.
3. ...
4. Ciesz się, że go rozgryzłeś.
5. Przystosuj kod do kształtu poniższej architektury i dodaj do niego nową logikę:
5.1. Spraw, aby klasa AbstractRobot była abstrakcyjna. Następnie przenieś logikę działań attack i defend z klasy Robot do klasy AbstractRobot.
5.2. Edytuj klasę Robot, aby użyć klasy AbstractRobot.
5.3. Rozszerz klasę BodyPart o nową część ciała (element) robota: BodyPart.CHEST.
5.4. Dodaj nową część ciała do implementacji interfejsów CanAttack i CanDefend (w klasie AbstractRobot).

Wymagania:

Klasa AbstractRobot musi być abstrakcyjna.
Klasa AbstractRobot musi implementować interfejsy CanAttack i CanDefend.
Klasa Robot musi dziedziczyć klasę AbstractRobot.
Logika definiująca to, jak zachowuje się Robot, musi być w klasie AbstractRobot.
Klasa BodyPart musi zawierać i inicjalizować finalną, statyczną zmienną BodyPart o nazwie CHEST.
Nowa część musi zostać dodana do logiki metod logic i attack w klasie AbstractRobot.

package pl.codegym.task.task13.task1328; /* Walki robotów */ public class Solution { public static void main(String[] args) { Robot amigo = new Robot("Amigo"); Robot enemy = new Robot("Wróg"); doMove(amigo, enemy); doMove(amigo, enemy); doMove(enemy, amigo); doMove(amigo, enemy); doMove(enemy, amigo); doMove(amigo, enemy); doMove(enemy, amigo); doMove(amigo, enemy); } public static void doMove(AbstractRobot robotFirst, AbstractRobot robotSecond) { BodyPart attacked = robotFirst.attack(); BodyPart defended = robotFirst.defend(); System.out.println(String.format("%s zaatakował %s: zaatakowano jego %s i zdołano obronić jego %s", robotFirst.getName(), robotSecond.getName(), attacked, defended)); } interface CanAttack { BodyPart attack(); } interface CanDefend { BodyPart defend(); } abstract class AbstractRobot implements CanAttack, CanDefend { // logika jak zachowuje się robot abstract String getName(); //abstract logic(); // Req.6 ???? } public class Robot extends AbstractRobot { String name; // konstruktor name dla obiektów robot public Robot (String name) { this.name = name; } @Override public String getName() { return name; } @Override public BodyPart attack() { return null; } @Override public BodyPart defend() { return null; } } public static class BodyPart { final static BodyPart CHEST = new BodyPart("Chest"); final static BodyPart HEAD = new BodyPart("Head"); String bodyPart; public BodyPart(String bodyPart) { this.bodyPart = bodyPart; } } }

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Guadalupe Gagnon

Poziom 37 , Tampa, United States

28 września 2021, 20:09

rozwiązanie

why do you have classes inside the Solution class? The task doesn't tell you to do that. I would recommend resetting the task and starting over as the Solution class should only have the original 29 or so lines of code in it.

Robert

Poziom 20 , Debica, Poland

29 września 2021, 14:59

Good point. I moved bracket 85 to line 29. Copy reset paste, and it shows me strange messages and 😅 I just realized that I have already written classes and interfaces by default in the assignment. 🤔 And I was thinking so long. What I must put in to this abstract class. Some logic? pffff... Surely not at this level. Thanks, Guadalupe.

Guadalupe Gagnon

Poziom 37 , Tampa, United States

29 września 2021, 15:42

The above code won't pass the task but I just wanted to explain the error you are receiving. It is a little above your level but it wouldn't hurt to be introduced to the concept at this point. Later lessons go over it and you will already have a head start: When a class is contained inside of a class, and that contained class is not static, it means that the contained class linked to the outer class. More specifically any object of the contained class is linked to an object of the outer class. You NEED an object of the outer class to make an object of the contained class. So, to make the above code valid, you would first have to make a Solution object (the outer class) and then use that object to create a Robot object (the contained class). Here is what that looks like in code:

public static void main(String[] args) {
   Solution obj = new Solution();
   Robot amigo = obj.new Robot("Amigo");
   Robot enemy = obj.new Robot("Wróg");
   // rest of code
}

Now the above code will compile and run. The task doesn't want you to do this though, and all the information I provided is just to address what you are experiencing in the code you created. To actually solve the task make sure that you use the classes that are already provided in separate files. If you need any help let me know.

Guadalupe Gagnon

Poziom 37 , Tampa, United States

29 września 2021, 16:31

Also recently I set up a discord channel for Java students on codegym. Its brand new, so there really isn't anyone on it, but I am hoping that it will grow soon. Feel free to join: Java Discord Channel

Robert

Poziom 20 , Debica, Poland

30 września 2021, 18:50

Thanks, i'm in. It is like nesting class? I saw in book topic like this, but not read about it deeply yet.

Guadalupe Gagnon

Poziom 37 , Tampa, United States

30 września 2021, 19:10

You could call it nesting classes. A very common one that you have probably used is Iterator. The type Iterator is actually an interface but many container classes (list, map, set) implement a method that returns an Iterator object that would be a class nested within as a standard was of accessing the objects data one at a time in order. Take this bit of code for example:

public static void main(String[] args) throws IOException {
   List<Integer> intList = new ArrayList<>();
   intList.add(1); intList.add(5); intList.add(3);

   Vector<String> strVec = new Vector<>();
   strVec.add("one"); strVec.add("five"); strVec.add("three");

   Set<Double> dblSet = new HashSet<>();
   dblSet.add(3.45); dblSet.add(2.87);dblSet.add(1.6);

   Map<String, Integer> stInMap = new Hashtable<>();
   stInMap.put("one", 1); stInMap.put("five", 5);stInMap.put("three", 3);
}

If I wanted to write code to print the values contained in each of these four objects: The 2 lists I could simply create a for loop that starts at an int i at 0, gets the index of i each loop cycle from the list, then increases i by one. Now for the Set and the Map I wouldn't be able to do this. For the set there is no easy way to print each value contained. For the map, assuming I had the keys, I could print each value; however if I didn't have the keys printing the contained values would be a problem. This is why the Iterator was invented, to access values of any container type object. Take this bit of code as a continuation of the above example:

static void print(Iterator x){
   if(x.hasNext()) System.out.print(x.next());

   while(x.hasNext()) System.out.print(" " + x.next());

   System.out.println();
}

Now you can pass all for of those objects to this one print() method and get the outputs. The Iterator standardized access to the containers

Guadalupe Gagnon

Poziom 37 , Tampa, United States

30 września 2021, 19:10

here is the full code of my last post:

public class Solution {
    public static void main(String[] args) throws IOException {
        List<Integer> intList = new ArrayList<>();
        intList.add(1); intList.add(5); intList.add(3);

        Vector<String> strVec = new Vector<>();
        strVec.add("one"); strVec.add("five"); strVec.add("three");

        Set<Double> dblSet = new HashSet<>();
        dblSet.add(3.45); dblSet.add(2.87);dblSet.add(1.6);

        Map<String, Integer> stInMap = new Hashtable<>();
        stInMap.put("one", 1); stInMap.put("five", 5);stInMap.put("three", 3);

        print(intList.iterator());
        print(strVec.iterator());
        print(dblSet.iterator());
        print(stInMap.entrySet().iterator());
    }

    static void print(Iterator x){
        if(x.hasNext())
            System.out.print(x.next());

        while(x.hasNext())
            System.out.print(" " + x.next());

        System.out.println();
    }
}

Robert

Poziom 20 , Debica, Poland

3 października 2021, 18:57

Inside print method, there are two loops, if the passed argument does not contain index, then is moving from 'if' to 'while' loop?

Guadalupe Gagnon

Poziom 37 , Tampa, United States

4 października 2021, 15:16

only one loop. The first if statement checks if there is a value, which it prints. The while loop while then print every other value starting with a space. That just prints it nicely on one line.