userexit Posts - Answer Overflow

public class ThreadComposition implements Runnable {
    private String name;
    private final Thread thread;

    public ThreadComposition(String name) {
        this.name = name;
        thread = new Thread(this);
    }

    @Override
    public void run() {
        for (int i=0; i<10; i++) {
            for (int j=0; j<50000; j++) {
                System.out.println("Thread " + name + " running");
            }
        }
    }

    public void start() {
        thread.start();
    }
}

public class ThreadComposition implements Runnable {
    private String name;
    private final Thread thread;

    public ThreadComposition(String name) {
        this.name = name;
        thread = new Thread(this);
    }

    @Override
    public void run() {
        for (int i=0; i<10; i++) {
            for (int j=0; j<50000; j++) {
                System.out.println("Thread " + name + " running");
            }
        }
    }

    public void start() {
        thread.start();
    }
}

4 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/21/2024 in #java-help

Help decoupling a presenter class in multiple classes

4 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/21/2024 in #java-help

Is it good practice to have 2 DTO's. one for database, one for application.

Im having an error as my DTO constructor can throw exceptions if the data introduced to it is invalid, but doing so means I can't create DTO's in DAO without handling these exceptions, but the DAO layer is not supposed to handle exceptions

4 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/21/2024 in #java-help

Should I decouple my presenter in multiple ones ?

6 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/20/2024 in #java-help

Help improving this code

ok so when i query a favorite row i know its id because its already been inserted, problem arises when i try inserting a favoritedto that i made in the program, i cant know what the id will be for it, but i dont have to either because the add method of my dao will just insert it and sql will generate a key for it. problem is when im trying to save a favorite ride i need to pass a favoritedto as argument but a favoritedto requires a id to be constructed, so i just put garbage number to construct it, there is no issue then all fine. problem is i dont think this is good written and i would refer to this as spaghetti code

195 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/20/2024 in #java-help

How could I simplify this

public interface Dao<K, S extends Key<K>> { void update(S item); void insert(S item); void delete(K key); S select(K key); List<S> selectAll(); } public interface Dao<K, T, S extends Key<K, T>> { void update(S item); void insert(S item); void delete(K key1, T key2); S select(K key1, T key2); List<S> selectAll(); } public interface Dao<K, T, I S extends Key<K, T, I>> { void update(S item); void insert(S item); void delete(K key1, T key2, I key3); S select(K key1, T key2, I key3); List<S> selectAll(); }

87 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/19/2024 in #java-help

HELP HANDLING ERRORS IN MVP

Design Pattern: MVP -> MODEL-VIEW-PRESENTER Interaction with user - presenter calls logic on model - model updates presenter - presenter updates view and/or calls new logic on model now assume there is code in model that throws errors (parameter validation for example): in presenter: try { model.doSomething(); } catch (error) { view.showError(blabla); } is it better this way, or is it better like this: in presenter: model.doSomething(); in model: if (name.length < 2) { notifyObservers(ModelEvent.NOT_ENOUGH_NAME_LENGTH); return; } then in presenter: update(ModelEvent event) { switch (event) { case NOT_ENOUGH_NAME_LENGTH: view.showError(blabla); break; } }

50 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/18/2024 in #java-help

Help Project MVP Layout

I was thinking of this layout: Presenter class that will handle interaction between model and view ViewController class with methods to interact with the UI Model package with: - Repository that is going to contact the database and get me the needed information - Dijkstra class that is going to handle calculating shortest path between 2 nodes. Instantiating View => generating the UI Instantiating Presenter => initializing the View with data that I get from the model, adding presenter as a button handler for view and adding presenter as an observer of Model Instantiating Model => creating an instance of dijkstra and repository. any idea how to optimize this ?

4 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/18/2024 in #java-help

Help optimize this dijkstra algorithm:

public static void dijkstra(Set<Node> graph, Node start, Node end) {
        start.setDistance(0);
        Set<Node> visited = new HashSet<>();
        dijkstraHelper(graph, visited, start, end);
    }

    public static void dijkstraHelper(Set<Node> unvisited, Set<Node> visited, Node currentNode, Node end) {
        if (visited.contains(end)) {
            Node prevNode = end;
            System.out.println(prevNode);
            while (prevNode.getPreviousNode() != null) {
                System.out.println(prevNode.getPreviousNode());
                prevNode = prevNode.getPreviousNode();
            }
            return;
        }

        Map<Node, Integer> neighbours = currentNode.getAdjacentNodes();
        neighbours.forEach((node, distance) -> {
            if (unvisited.contains(node)) {
                int computeDistance = distance + currentNode.getDistance();
                if (computeDistance <= node.getDistance()) {
                    node.setDistance(computeDistance);
                    node.setPrevNode(currentNode);
                }
            }
        });

        unvisited.remove(currentNode);
        visited.add(currentNode);

        AtomicReference<Node> nextNode = new AtomicReference<>();
        neighbours.forEach((node, integer) -> {
            if (nextNode.get() == null && unvisited.contains(node)) {
                nextNode.set(node);
            } else if (unvisited.contains(node) && node.getDistance() < nextNode.get().getDistance()){
                nextNode.set(node);
            }
        });

        dijkstraHelper(unvisited, visited, nextNode.get(), end);
    }

public static void dijkstra(Set<Node> graph, Node start, Node end) {
        start.setDistance(0);
        Set<Node> visited = new HashSet<>();
        dijkstraHelper(graph, visited, start, end);
    }

    public static void dijkstraHelper(Set<Node> unvisited, Set<Node> visited, Node currentNode, Node end) {
        if (visited.contains(end)) {
            Node prevNode = end;
            System.out.println(prevNode);
            while (prevNode.getPreviousNode() != null) {
                System.out.println(prevNode.getPreviousNode());
                prevNode = prevNode.getPreviousNode();
            }
            return;
        }

        Map<Node, Integer> neighbours = currentNode.getAdjacentNodes();
        neighbours.forEach((node, distance) -> {
            if (unvisited.contains(node)) {
                int computeDistance = distance + currentNode.getDistance();
                if (computeDistance <= node.getDistance()) {
                    node.setDistance(computeDistance);
                    node.setPrevNode(currentNode);
                }
            }
        });

        unvisited.remove(currentNode);
        visited.add(currentNode);

        AtomicReference<Node> nextNode = new AtomicReference<>();
        neighbours.forEach((node, integer) -> {
            if (nextNode.get() == null && unvisited.contains(node)) {
                nextNode.set(node);
            } else if (unvisited.contains(node) && node.getDistance() < nextNode.get().getDistance()){
                nextNode.set(node);
            }
        });

        dijkstraHelper(unvisited, visited, nextNode.get(), end);
    }

9 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/17/2024 in #java-help

Help implementing DJIKSTRA ALGORITHM

I have a Graph class that contains a Set of nodes, I define a node to have a name and adjacent nodes. The only thing im struggling with is: lets say we have this: A ---- B ---- C | | D ---- E Node D has name "D" and its adjacent nodes are E and A. How can I adapt my class to hold the distance to node E and A ? I have thought of modifying my node class to have a attribute distance to Parent, then Node E distance to parent is 1 but what if it has multiple parents as in what if a node F was connected to it

4 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/17/2024 in #java-help

How can I do this MVP model view presenter

Trying to implement this design pattern but need some help, my view class extends Application and has a start method inside it how can I access this and launch the view through my main class ?

58 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/17/2024 in #java-help

Can anyone explain this error message

Explain this error message please:

27 replies

JCHJava Community | Help. Code. Learn.

•Created by userexit on 5/16/2024 in #java-help

What is the benefit of using the Singleton pattern like this:

public static ConfigManager getInstance() {
        return ConfigManagerHolder.INSTANCE;
    }

    private static class ConfigManagerHolder {

        private static final ConfigManager INSTANCE = new ConfigManager();
    }
}

public static ConfigManager getInstance() {
        return ConfigManagerHolder.INSTANCE;
    }

    private static class ConfigManagerHolder {

        private static final ConfigManager INSTANCE = new ConfigManager();
    }
}

What is the benefit of having an internal class compared to just returning a new ConfigManager()

33 replies

Gaming

Programming