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我想將列表轉換爲數組,但我得到一個錯誤,我找不出原因。我正在採取當前的時間,並且在for循環中,我將今天的其餘時間放到列表中。當我嘗試將其更改爲數組時,出現錯誤。我嘗試,因爲後來我用的是陣列中的JCombobox
方法toArray()不工作在列表
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.GregorianCalendar;
import java.util.Calendar;
public class Frame extends JFrame implements ActionListener{
//JFrame elements
private JButton btnSetTime;
private JLabel lblTitle;
private JComboBox comboTime;
//Standard elements
private Timer tillPopup, tillShutdown;
Calendar calendar = new GregorianCalendar();
int hour = (calendar.get(Calendar.HOUR_OF_DAY));
List times = createDropdown(hour);
// Convert ArrayList to array which can be used in the combobox
String[] dropdownElements = times.toArray();
String[] a = {"a","b"};
public Frame(){
setLayout(new FlowLayout());
//Labels
lblTitle = new JLabel("Deze applicatie sluit u computer automatisch af om het energieverbruik te verminderen.");
//Combobox
comboTime = new JComboBox(a);
comboTime.setSelectedIndex(0);
//Button
btnSetTime = new JButton("Zet afsluittijd");
//Timers
//tillPopup = new Timer(this);
//tillShutdown = new Timer(this);
//Add elements to Frame
add(lblTitle);
add(comboTime);
add(btnSetTime);
//Add actionListeners
btnSetTime.addActionListener(this);
setSize(500,300);
setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
private List createDropdown(int hour){
List availableHours = new List();
for(int i = hour; i <=24; i++){
if (i != 24){
availableHours.add(i + ":00");
}
else if(i == 24){
availableHours.add("00:00");
}
}
return availableHours;
}
public void actionPerformed(ActionEvent e){
if (e.getSource() == btnSetTime){
Object popupTime = comboTime.getSelectedItem();
System.out.println(popupTime);
}
}
}
我碰到下面的錯誤要做到這一點:
Frame.java:21: error: cannot find symbol
String[] dropdownElements = times.toArray();
^
symbol: method toArray()
location: variable times of type List
如何列表我回來從method createDropdown
更改到一個數組和爲什麼我做錯了?
您的解決方案效果很好,但我不明白爲什麼我必須在其後面放置''。 util和awt'list'有什麼區別。 PS。我是一個初學者 –
@GertKommer''代表一個實際的類型參數。你需要把它放在因爲java.util.List是泛型類型。你可以從http://docs.oracle.com/javase/tutorial/java/generics/ –
@GertKommer瞭解更多關於泛型的知識或者對於快速的基本介紹,我寫了一篇博文 - http://rjcodeblog.wordpress .com/2013/09/28/java-generics-a-basic-introduction /。這會給你一個快速的開始。 –