java - 使用两个不同的构造函数创建单个对象

Question

这个问题已经有答案了:

How to avoid constructor code redundancy in Java? (4 个回答)

已关闭 5 年前。

我有一个 Card 类，其中包含两个构造函数，正如您在下面的代码中看到的那样。问题是每个 Card 对象接受 2 个字符串和 2 个图像，因为我想保存这些对象，所以我必须将图像的路径保存为字符串，然后检索它们，即 2 个构造函数。然而，使用一些打印语句我发现每当检索一张卡时，都会创建 2 个单独的对象:一个普通的对象和另一个为空的对象。我知道发生这种情况是因为我使用第二个构造函数中的第一个构造函数创建了一张新卡。有没有办法避免这种情况，这样我就不会拥有两个单独的对象？如果可能的话，我想找到一种只使用一个构造函数的方法。这是我的类:

Card.java:

package com.spdesigns.dokkancardspreview.model;

import javafx.scene.image.Image;

public class Card {

private String mName;
private String mDescription;
private Image mMainImage;
private Image mSecondaryImage;
private String mMainImagePath;
private String mSecondaryImagePath;

public Card(String name, String description, Image mainImage, Image secondaryImage) {
    mName = name;
    mDescription = description;
    mMainImage = mainImage;
    mSecondaryImage = secondaryImage;
}

public Card(String name, String description , String mainImagePath, String secondaryImagePath) {
   Card newCardToAdd =  new Card(name,description,new Image(mainImagePath),new Image(secondaryImagePath));
}

@Override
public String toString() {
    return mName + " | " + mDescription;
}

public Image getmMainImage() {
    return mMainImage;
}

public Image getmSecondaryImage() {
    return mSecondaryImage;
}

public String getName() {
    return mName;
}

public String getDescription() {
    return mDescription;
}
}

home.java:

package com.spdesigns.dokkancardspreview.controllers;

import com.spdesigns.dokkancardspreview.model.Card;

import javafx.beans.property.ListProperty;
import javafx.beans.property.SimpleListProperty;
import javafx.collections.FXCollections;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.ListView;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;

import java.io.*;
import java.util.List;
import java.net.URL;
import java.util.ArrayList;
import java.util.ResourceBundle;

public class home implements Initializable {

private Card hit = new Card("Hit","Expanding Possibility",
        new Image("/images/hit_main.jpg") , new Image("/images/hit_secondary.jpg"));

private Card goku = new Card("Goku SSJ3","Everlasting legend",
        new Image("/images/gokussj3_main.jpg") , new Image("/images/gokussj3_secondary.jpg"));

private boolean clickedAgain = false;

@FXML
private Button arrowButton;
@FXML
private ImageView imageView;

@FXML
private ImageView arrow;

@FXML
private ListView listView;

protected List<Card> testingList = new ArrayList<Card>();

    protected ListProperty<Card> listProperty = new SimpleListProperty<Card>();


@Override
public void initialize(URL location, ResourceBundle resources) {
    addCard(hit);
    addCard(goku);
    //testingList.add("test2");

    listView.itemsProperty().bind(listProperty);
    // wrapping our list in an observable list and then pass that observableList to the ListProperty isntance
    listProperty.set(FXCollections.observableArrayList(testingList));

    // Handle listView selection changes
    listView.getSelectionModel().selectedItemProperty().addListener(((observable, oldValue, newValue) -> {
        Card currentlySelectedCard = listProperty.get(listView.getSelectionModel().getSelectedIndex());
        System.out.printf("ListView item clicked! Value retrieved: %s\n", currentlySelectedCard);
        imageView.setImage(new Image(currentlySelectedCard.getmMainImage().impl_getUrl()));
        arrow.setVisible(true);
        arrowButton.setVisible(true);
    }));

    arrow.translateYProperty().set(283f);
    arrowButton.translateYProperty().set(283f);
    arrow.setRotate(180);
    arrow.setVisible(false);
    arrowButton.setVisible(false);
}

public void handleShowDetails(ActionEvent actionEvent) {
    System.out.println("Button Clicked!");
    Card currentlySelectedCard = listProperty.get(listView.getSelectionModel().getSelectedIndex());
    if(clickedAgain) {
        imageView.setImage(new Image(currentlySelectedCard.getmMainImage().impl_getUrl()));
        arrow.setRotate(180);
        clickedAgain = false;
    } else {
        imageView.setImage(new Image(currentlySelectedCard.getmSecondaryImage().impl_getUrl()));
        arrow.setRotate(360);
        clickedAgain = true;
    }
}

// Saving
public void exportTo(String fileName) {
    try(
            FileOutputStream fos = new FileOutputStream(fileName);
            PrintWriter writer = new PrintWriter(fos);
    ){
        for(int i =0;i<testingList.size()-1;i++) {
            writer.printf("%s|%s|%s|%s\n",testingList.get(i).getName(),testingList.get(i).getDescription(),
                    testingList.get(i).getmMainImage().impl_getUrl(),testingList.get(i).getmSecondaryImage().impl_getUrl());
            System.out.println(testingList.get(i).toString());
        }
    } catch (IOException ioe) {
        System.out.printf("Problem saving: %s/n", fileName);
        ioe.printStackTrace();
    }
}

// Loading
public void importFrom(String fileName) {
    try(
            FileInputStream fis = new FileInputStream(fileName);
            BufferedReader reader = new BufferedReader(new InputStreamReader(fis));
    ){
        String line;
        while((line = reader.readLine()) != null) {
            String[] args = line.split("\\|");
            this.addCard(new Card(args[0],args[1],args[2],args[3]));
        }
    } catch (IOException ioe) {
        System.out.printf("Problem loading: %S\n" , fileName);
        ioe.printStackTrace();
    }
    int i = 0;
    for (Card card : testingList) {
        System.out.printf("%s loaded\n",testingList.get(i).toString());
        i++;
    }
    System.out.println("Loading Successful!");
}

public void addCard(Card card) {
    testingList.add(card);
}

// DEBUG purposes
public void printTestingList() {
    for (Card card : testingList) {
        System.out.println(card.toString());
    }
}
}

主.JAVA:

package com.spdesigns.dokkancardspreview;

import com.spdesigns.dokkancardspreview.controllers.home;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import java.io.File;

public class Main extends Application {

private home controller;
private File file = new File("CardsCollection.txt");

@Override
public void start(Stage primaryStage) throws Exception{
    FXMLLoader loader = new FXMLLoader(getClass().getResource("/fxml/home.fxml"));
    Parent root = loader.load();
    controller = loader.getController();
    primaryStage.setTitle("Dokkan Battle Card Preview");
    primaryStage.setScene(new Scene(root, 900, 700));
    primaryStage.setResizable(false);
    // Loading cards
    primaryStage.show();
    try {
        if(!file.exists()) {
            file.createNewFile();
        }
        controller.importFrom("CardsCollection.txt");
    } catch (NullPointerException npe) {
        System.out.println("Error loading file!");
        npe.printStackTrace();
    }
}

@Override
public void stop() {
    System.out.println("App is closing!");
    // Saving before exiting
    try {
        controller.exportTo("CardsCollection.txt");
    } catch (NullPointerException npe) {
        System.out.println("Problem saving file!");
        npe.printStackTrace();
    }
   // controller.printTestingList();
}

public static void main(String[] args) {
    launch(args);
}
}

Answer 1

改变

public Card(String name, String description , String mainImagePath, String secondaryImagePath) {
   Card newCardToAdd =  new Card(name,description,new Image(mainImagePath),new Image(secondaryImagePath));
}

至

public Card(String name, String description , String mainImagePath, String secondaryImagePath) {
   this(name,description,new Image(mainImagePath),new Image(secondaryImagePath));
}