So löschen Sie ein Element aus Array-Liste Java-Eclipse

Question

Hallo Ich habe eine einfache Liste hier für Lebensmittel, die mit dem Hinzufügen von ihnen zu einer Gesamtkosten befassen. (Wie eine Registrierkasse) Ich habe Probleme, einen Löschknopf zu machen, um Gegenstände von der Liste zu löschen und von den Gesamtkosten zu subtrahieren. Bitte helfen Sie mir, ich weiß nicht, wo ich anfangen soll. Hier ist der Code.

// Import Core Java packages 
import java.awt.*; 
import java.awt.event.*; 

public class FastFood extends Frame { 

/** 
* 
*/ 
private static final long serialVersionUID = 1L; 
// Initial Frame size 
static final int WIDTH = 400;    // frame width 
static final int HEIGHT = 300;    // frame height 

// Arrays of selection items 
static final String[] FRUIT_FOODS = {"Pear", "Apple", "Peach", "Banana"}; 
static final int[] FRUIT_FOODS_PRICE = {79, 69, 89, 59}; 
static final String[] BEVERAGE_DRINKS = {"Soda", "Coffee", "Milk", "Water"}; 
static final int[] BEVERAGE_DRINKS_PRICE = {79, 95, 85, 65}; 
static final String[] JUNK_FOODS = {"Burger", "Hotdog", "Fries", "Pizza"}; 
static final int[] JUNK_FOODS_PRICE = {199, 150, 99, 299}; 
static final String[] DESSERTS = {"Ice cream", "Pie", "Cake", "Donut"}; 
static final int[] DESSERTS_PRICE = {149, 249, 299, 99}; 

// List and Button control 
List fruitFoodList; 
List beverageList; 
List junkFoodList; 
List dessertList; 
List itemsOrderedList; 
Button addFruitFood; 
Button addBeverage; 
Button addJunkFood; 
Button addDessert; 
Button deleteItem; 

// Total amount and display 
Label amountLabel; 
int amount = 0; 

/** 
* Constructor 
*/ 
public FastFood() { 
    setTitle("Fast Food To Go"); 
    setLayout(new BorderLayout()); 

    // create display for item selection 
    Panel itemPanel = new Panel(new GridLayout(2, 1)); 
    add(itemPanel, BorderLayout.CENTER); 

    // create display and control for junk food selection items 
    Panel junkFoodPanel = new Panel(new BorderLayout()); 
    itemPanel.add(junkFoodPanel); 
    Label junkFood = new Label("Fast Food Items", Label.CENTER); 
    junkFood.setForeground(Color.red); 
    junkFoodPanel.add(junkFood, BorderLayout.NORTH); 
    junkFoodList = new List(); 
    for(int i=0; i<JUNK_FOODS.length; i++) { 
     junkFoodList.add(JUNK_FOODS[i]+ " $" + (float)JUNK_FOODS_PRICE[i]/100); 
    } 
    junkFoodPanel.add(junkFoodList, BorderLayout.CENTER); 
    Panel buttonPanel = new Panel(new FlowLayout(FlowLayout.CENTER)); 
    junkFoodPanel.add(buttonPanel, BorderLayout.SOUTH); 
    addJunkFood = new Button("Get Food Item"); 
    buttonPanel.add(addJunkFood); 

    //create a display for fruit items 
    Panel fruitFoodPanel = new Panel(new BorderLayout()); 
    itemPanel.add(fruitFoodPanel); 
    Label fruitFood = new Label("Fruit Items", Label.CENTER); 
    fruitFood.setForeground(Color.red); 
    fruitFoodPanel.add(fruitFood, BorderLayout.NORTH); 
    fruitFoodList = new List(); 
    for(int i=0; i<FRUIT_FOODS.length; i++) { 
     fruitFoodList.add(FRUIT_FOODS[i]+ " $" + (float)FRUIT_FOODS_PRICE[i]/100); 
    } 
    fruitFoodPanel.add(fruitFoodList, BorderLayout.CENTER); 
    buttonPanel = new Panel(new FlowLayout(FlowLayout.CENTER)); 
    fruitFoodPanel.add(buttonPanel, BorderLayout.SOUTH); 
    addFruitFood = new Button("Get Fruit"); 
    buttonPanel.add(addFruitFood); 

    // create display and control for dessert selection items 
    Panel dessertPanel = new Panel(new BorderLayout()); 
    itemPanel.add(dessertPanel); 
    Label dessertLabel = new Label("Dessert Items", Label.CENTER); 
    dessertLabel.setForeground(Color.red); 
    dessertPanel.add(dessertLabel, BorderLayout.NORTH); 
    dessertList = new List(); 
    for(int i=0; i<DESSERTS.length; i++) { 
     dessertList.add(DESSERTS[i]+ " $" + (float)DESSERTS_PRICE[i]/100); 
    } 
    dessertPanel.add(dessertList, BorderLayout.CENTER); 
    buttonPanel = new Panel(new FlowLayout(FlowLayout.CENTER)); 
    dessertPanel.add(buttonPanel, BorderLayout.SOUTH); 
    addDessert = new Button("Get Dessert Item"); 
    buttonPanel.add(addDessert); 

    //create a display for Beverages 
    Panel beveragePanel = new Panel(new BorderLayout()); 
    itemPanel.add(beveragePanel); 
    Label beverage = new Label("Beverages", Label.CENTER); 
    beverage.setForeground(Color.red); 
    beveragePanel.add(beverage, BorderLayout.NORTH); 
    beverageList = new List(); 
    for(int i=0; i<BEVERAGE_DRINKS.length; i++) { 
     beverageList.add(BEVERAGE_DRINKS[i]+ " $" + (float)BEVERAGE_DRINKS_PRICE[i]/100); 
    } 
    beveragePanel.add(beverageList, BorderLayout.CENTER); 
    buttonPanel = new Panel(new FlowLayout(FlowLayout.CENTER)); 
    beveragePanel.add(buttonPanel, BorderLayout.SOUTH); 
    addBeverage = new Button("Get Beverage"); 
    buttonPanel.add(addBeverage); 


    // create display and control for items ordered and amount 
    Panel orderedPanel = new Panel(new BorderLayout()); 
    add(orderedPanel, BorderLayout.EAST); 

    // create display and control for items ordered 
    Panel itemsOrderedPanel = new Panel(new BorderLayout()); 
    orderedPanel.add(itemsOrderedPanel, BorderLayout.CENTER); 
    Label itemsOrdered = new Label("Items Ordered", Label.CENTER); 
    itemsOrdered.setForeground(Color.red); 
    itemsOrderedPanel.add(itemsOrdered, BorderLayout.NORTH); 
    itemsOrderedList = new List(); 
    itemsOrderedPanel.add(itemsOrderedList, BorderLayout.CENTER); 
    buttonPanel = new Panel(new FlowLayout(FlowLayout.CENTER)); 
    itemsOrderedPanel.add(buttonPanel, BorderLayout.SOUTH); 
    deleteItem = new Button("Delete Ordered Item"); 
    buttonPanel.add(deleteItem); 

    // create display for amount 
    Panel amountPanel = new Panel(new BorderLayout()); 
    orderedPanel.add(amountPanel, BorderLayout.SOUTH); 
    Label totalLabel = new Label("Total Amount: "); 
    amountPanel.add(totalLabel, BorderLayout.WEST); 
    amountLabel = new Label("$0.00"); 
    amountPanel.add(amountLabel, BorderLayout.CENTER); 

    // create and add list selection listener 
    SelectionListener selListener = new SelectionListener(); 
    junkFoodList.addActionListener(selListener); 
    dessertList.addActionListener(selListener); 
    fruitFoodList.addActionListener(selListener); 
    beverageList.addActionListener(selListener); 

    // create and add button listener 
    ButtonListener buttonListener = new ButtonListener(); 
    addJunkFood.addActionListener(buttonListener); 
    addDessert.addActionListener(buttonListener); 
    addFruitFood.addActionListener(buttonListener); 
    addBeverage.addActionListener(buttonListener); 
} // end of constructor 

/** 
* Listener class for list selection 
*/ 
class SelectionListener implements ActionListener { 
    public void actionPerformed(ActionEvent event) { 
     String selectedItem; 
     int selectedIndex; 
     int itemPrice; 

     if(event.getSource() == junkFoodList) { // select item from junk food list 
      selectedIndex = junkFoodList.getSelectedIndex(); 
      selectedItem = junkFoodList.getSelectedItem(); 
      itemPrice = JUNK_FOODS_PRICE[selectedIndex]; 
      addOrderedItem(selectedItem, itemPrice); 
     } 
     else if(event.getSource() == dessertList) { // select item from dessert list 
      selectedIndex = dessertList.getSelectedIndex(); 
      selectedItem = dessertList.getSelectedItem(); 
      itemPrice = DESSERTS_PRICE[selectedIndex]; 
      addOrderedItem(selectedItem, itemPrice); 
     } 
     else if(event.getSource() == fruitFoodList) { // select item from dessert list 
      selectedIndex = fruitFoodList.getSelectedIndex(); 
      selectedItem = fruitFoodList.getSelectedItem(); 
      itemPrice = FRUIT_FOODS_PRICE[selectedIndex]; 
      addOrderedItem(selectedItem, itemPrice); 
     } 
     else if(event.getSource() == beverageList) { // select item from dessert list 
      selectedIndex = beverageList.getSelectedIndex(); 
      selectedItem = beverageList.getSelectedItem(); 
      itemPrice = BEVERAGE_DRINKS_PRICE[selectedIndex]; 
      addOrderedItem(selectedItem, itemPrice); 
     } 
    } 
} 

/** 
* Listener class for button selection 
*/ 
class ButtonListener implements ActionListener { 
    public void actionPerformed(ActionEvent event) { 
     String selectedItem; 
     int selectedIndex; 
     int itemPrice; 

     if(event.getSource() == addJunkFood) { // get item from junk food list 
      selectedIndex = junkFoodList.getSelectedIndex(); 
      if(selectedIndex >= 0) { 
       selectedItem = junkFoodList.getSelectedItem(); 
       itemPrice = JUNK_FOODS_PRICE[selectedIndex]; 
       addOrderedItem(selectedItem, itemPrice); 
      } 
     } 
     else if(event.getSource() == addDessert) { // get item from dessert list 
      selectedIndex = dessertList.getSelectedIndex(); 
      if(selectedIndex >= 0) { 
       selectedItem = dessertList.getSelectedItem(); 
       itemPrice = DESSERTS_PRICE[selectedIndex]; 
       addOrderedItem(selectedItem, itemPrice); 
      } 
     } 
     else if(event.getSource() == addFruitFood) { // get item from fruit food list 
      selectedIndex = fruitFoodList.getSelectedIndex(); 
      if(selectedIndex >= 0) { 
       selectedItem = fruitFoodList.getSelectedItem(); 
       itemPrice = FRUIT_FOODS_PRICE[selectedIndex]; 
       addOrderedItem(selectedItem, itemPrice); 
      } 
     } 
     else if(event.getSource() == addBeverage) { // get item from fruit food list 
      selectedIndex = beverageList.getSelectedIndex(); 
      if(selectedIndex >= 0) { 
       selectedItem = beverageList.getSelectedItem(); 
       itemPrice = BEVERAGE_DRINKS_PRICE[selectedIndex]; 
       addOrderedItem(selectedItem, itemPrice); 
      } 
     } 
    } 
} 

/** 
* method to add/delete an ordered item 
*/ 
void addOrderedItem(String item, int price) { 
    itemsOrderedList.add(item); 
    amount += price; 
    amountLabel.setText("$"+(float)amount/100); 
} 


/** 
* the main method 
*/ 
public static void main(String[] argv) { 
    // Create a frame 
    FastFood frame = new FastFood(); 
    frame.setSize(WIDTH, HEIGHT); 
    frame.setLocation(150, 100); 

    // add window closing listener 
    frame.addWindowListener(new WindowAdapter() { 
     public void windowClosing(WindowEvent event) { 
      System.exit(0); 
     } 
    }); 

    // Show the frame 
    frame.setVisible(true); 
} 

}

Answer 1

rate ich Ihnen wieder Ihren Code schreiben. Ein Fehler zu beachten, Sie versuchen, Objekte vom Typ Liste zu erstellen. Liste ist keine Klasse und kann nicht instanziiert werden, sie ist eine Schnittstelle, die zu implementierende Methoden enthält, aber diese Methoden enthalten keine Körper. Um java.util.List zu verwenden, müssen Sie es implementieren und dann die Methoden in der Schnittstelle implementieren, die die entsprechenden Körper bereitstellen. Wenn Sie eine Liste in irgendeiner Form benötigen, müssen Sie je nach Bedarf eine java.util.ArrayList oder java.util.LinkedList verwenden.

Abgesehen davon ist der Code, den Sie hier gepostet haben, zu lang, Sie finden am besten heraus, in welchem ​​Codeblock der Fehler enthalten ist und welche Ausnahmen oder Fehlermeldungen Sie erhalten.