这是我的arraylist类的代码; 包餐厅;
import java.util.ArrayList;
public class Controlclass {
public static void main(String[] args) {
// Create ArrayList for foodItems subclasses
ArrayList<Mains> MainsList = new ArrayList<Mains>();
//add items to the MainsList
Mains CurriedFriedRice = new Mains (" Curried fried rice ", 4.00, " Yummy curried fried rice " , 500);
Mains LambChopsWithCarrotPuree = new Mains (" Lamb chops with carrot puree ", 6.00, " Delicious Lamb chops with carrot puree " , 580);
Mains PadThaiNoodles = new Mains (" Pad Thai noodles ", 5.00, " Amazing thai noodles " , 480);
Mains SalmonAndAsparagusFajitas = new Mains (" Salmon and asparagus fajitas ", 4.90, " Fajita you will always come back for " , 450);
MainsList.add(CurriedFriedRice);
MainsList.add(LambChopsWithCarrotPuree);
MainsList.add(PadThaiNoodles);
MainsList.add(SalmonAndAsparagusFajitas);
for (Mains mains: MainsList){
System.out.println(mains);
}
这是我需要在这些arraylists中使用的GUI类;
*
public class TheFoodLoversLounge {
private final GridLayout layout; // layout of this frame
private JFrame frame;
private final JPanel buttonbar;
private final JPanel combobar;
private final JPanel receiptbar;
private final JComboBox<String> mainsc;
public class TheFoodLoversLounge {
private final GridLayout layout; // layout of this frame
private JFrame frame;
private final JPanel buttonbar;
private final JPanel combobar;
private final JPanel receiptbar;
private final JComboBox<String> starters;
private final JComboBox<String> mainsc;
private final JComboBox<String> dessert;
private final JButton getTotalPrice;
private final JLabel l2;
private final JLabel l3;
private final JLabel l4;
private final JLabel l5;
private final JLabel l6;
private final JLabel l7;
private final JLabel l8;
private final JLabel l9;
private final JLabel l10;
private final JLabel r1;
private final JLabel r2;
private final JLabel r3;
private final JLabel r4;
private final JLabel r5;
private final JLabel r6;
private final JLabel r7;
private final JLabel r8;
private final JLabel r9;
private Controlclass control;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
TheFoodLoversLounge window = new TheFoodLoversLounge();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public TheFoodLoversLounge() {
MAXTABLES=10;
MAXDINERS=10;
initialize();
control = new Controlclass();
layout = new GridLayout(0,1,0,5);
starters=new JComboBox<>();
mainsc=new JComboBox<>();
dessert=new JComboBox<>();
for (Starters starterI: control.StarterList){
starters.addItem(starterI.toString());
}
starters.setMaximumRowCount(5);
for (Mains mainsI: control.MainsList){
mainsc.addItem(mainsI.toString());
}
mainsc.setMaximumRowCount(5);
for (Dessert dessertI: control.DessertList){
dessert.addItem(dessertI.toString());
}
buttonbar= new JPanel(layout);
buttonbar.setBackground(Color.LIGHT_GRAY);
buttonbar.add(getTotalPrice); buttonbar.add(l10);
combobar= new JPanel(layout);
combobar.setBackground(Color.PINK);
combobar.add(l1); combobar.add(starters);
combobar.add(l2); combobar.add(mainsc);
combobar.add(l4); combobar.add(dessert);
private void initialize() {
frame = new JFrame();
frame.setLocationRelativeTo(null);
//frame.setResizable(false);
frame.setSize(768, 800);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private class TheListener implements ActionListener
{
// process text field events
@Override
public void actionPerformed(ActionEvent event)
{
String string = "";
double arr [];
Orders ord = new Orders();
if (event.getSource() ==getTotalPrice){
ord.diners= Integer.parseInt((String) diners.getItemAt(diners.getSelectedIndex()));
ord.tableno=Integer.parseInt((String) tableno.getItemAt(tableno.getSelectedIndex()));
ord.item[0]=starters.getItemAt(starters.getSelectedIndex());
// ord.qty[1]=
ord.rate[0]=control.StarterList.get(starters.getSelectedIndex()).price;
ord.item[1]=mainsc.getItemAt(mainsc.getSelectedIndex());
// ord.qty[2]=
ord.rate[1]=control.MainsList.get(mainsc.getSelectedIndex()).price;
ord.item[2]=dessert.getItemAt(dessert.getSelectedIndex());
// ord.qty[3]=
ord.rate[2]=control.DessertList.get(dessert.getSelectedIndex()).price;
}
}}}
* 每个人都可以忽略语法错误，因为它不是完整的代码，我只想专注于arraylist因为每次我尝试编译它时会给我以下错误，而实际代码在语法上是正确的。 线程“AWT-EventQueue-0”中的异常java.lang.Error：未解决的编译问题：
StarterList cannot be resolved or is not a field
MainsList cannot be resolved or is not a field
DessertList cannot be resolved or is not a field
DrinksList cannot be resolved or is not a field
FishList cannot be resolved or is not a field
StarterList cannot be resolved or is not a field
MainsList cannot be resolved or is not a field
DessertList cannot be resolved or is not a field
FishList cannot be resolved or is not a field
DrinksList cannot be resolved or is not a field
at Restaurant.TheFoodLoversLounge.<init>(TheFoodLoversLounge.java:121)
at Restaurant.TheFoodLoversLounge$1.run(TheFoodLoversLounge.java:91)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
这些是我得到的错误。我不知道如何解决这些问题。请有人帮我。不完整代码的原因是我的项目，我不敢冒险。所以来自你们的解决方案将受到高度赞赏。
答案 0 :(得分：1)
请勿在{{1}}方法中定义您的列表。将它们定义为成员并在构造函数中初始化它们。然后为每个列表编写getter方法。
main最后，使用getter方法访问列表。
public class Controlclass {
private ArrayList<Mains> MainsList;
public ControlClass() {
MainsList = new ArrayList<Mains>()
}
public ArrayList<Mains> getMainsList() {
return MainsList;
}
}
答案 1 :(得分：1)
Controlclass不提供对您在ArrayList方法中定义的任何main的任何访问权限（并且对您的问题有很大的暗示）。
首先在Controlclass和提供public getter中定义实例字段，以允许他们访问这些字段（通过您可以控制的方法 - 例如，您可以返回不可变列表或复制返回之前列表）
import java.util.ArrayList;
import java.util.List;
public class Controlclass {
private List<...> starterList;
private List<...> mainsList;
private List<...> dessertList;
private List<...> drinksList;
private List<...> fishList;
public static void main(String[] args) {
Controlclass controlClass = new Controlclass();
}
public Controlclass() {
starterList = new ArrayList<>(25);
mainsList = new ArrayList<>(25);
dessertList = new ArrayList<>(25);
drinksList = new ArrayList<>(25);
fishList = new ArrayList<>(25);
// Populate the values...
}
public List<...> getStarterList() {
return starterList;
}
public List<...> getMainsList() {
return mainsList;
}
public List<...> getDessertList() {
return dessertList;
}
public List<...> getDrinksList() {
return drinksList;
}
public List<...> getFishList() {
return fishList;
}
}
（ps你需要用适当的泛型替换<...>，我真的不想深入研究所有代码来解决这个问题）
接下来将Controlclass的实例传递给其他类
public class TheFoodLoversLounge {
//...
private Controlclass control;
public TheFoodLoversLounge(Controlclass control) {
this.control = control
//...
最后，请使用Controlclass
for (Starters starterI: control.getStarterList()) {
starters.addItem(starterI.toString());
}
（并且让你的思想成为程序的主要切入点，有两个main方法将会非常混乱）