从arrayList添加到Jlist时出现错误

Question

我正在尝试制作一个程序，该程序需要分级的学生人数，然后获取x个等级并按升序对其进行冒泡排序。

我不知道如何将arraylist中的等级添加到jlist并输出它。 这是我的错误：

Unresolved compilation problem: 
    The method setListData(Integer[]) in the type JList<Integer> is not applicable for the arguments (Object[]) 

这是我的代码：

import java.awt.EventQueue; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.util.ArrayList; 

import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JTextField; 
import javax.swing.JButton; 
import javax.swing.JList; 

public class bubbleSwing { 

    private JFrame frame; 
    private JTextField inputNoOfGrades; 
    private JTextField inputGrades; 
    private String inputStr; 
    private JLabel tvNoOfGrades; 
    private JButton btnNoOfGrades; 
    private JLabel tvGrades; 
    private JButton btnGrades; 
    private JButton btnSort; 
    private JList<Integer> list; 

    ArrayList<Integer> grades = new ArrayList<Integer>(); 



    private int numOfGrades; 
    private int inputGradesInt; 

    /** 
    * Launch the application. 
    */ 
    public static void main(String[] args) { 
     EventQueue.invokeLater(new Runnable() { 
      public void run() { 
       try { 
        bubbleSwing bubbleSwing = new bubbleSwing(); 
        bubbleSwing.frame.setVisible(true); 

       } catch (Exception e) { 
        e.printStackTrace(); 
       } 

      } 
     }); 

    } 

    /** 
    * Create the application. 
    */ 
    public bubbleSwing() { 
     initialize(); 
    } 

    /** 
    * Initialize the contents of the frame. 
    */ 
    private void initialize() { 
     frame = new JFrame(); 
     frame.setBounds(100, 100, 450, 300); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.getContentPane().setLayout(null); 

     tvNoOfGrades = new JLabel("New label"); 
     tvNoOfGrades.setBounds(10, 11, 150, 29); 
     frame.getContentPane().add(tvNoOfGrades); 

     tvGrades = new JLabel("New label"); 
     tvGrades.setBounds(170, 11, 150, 29); 
     frame.getContentPane().add(tvGrades); 

     inputNoOfGrades = new JTextField(); 
     inputNoOfGrades.setBounds(10, 51, 86, 20); 
     frame.getContentPane().add(inputNoOfGrades); 
     inputNoOfGrades.setColumns(10); 

     inputGrades = new JTextField(); 
     inputGrades.setBounds(158, 51, 86, 20); 
     frame.getContentPane().add(inputGrades); 
     inputGrades.setColumns(10); 

     btnNoOfGrades = new JButton("Submit"); 
     btnNoOfGrades.setBounds(10, 82, 89, 23); 
     frame.getContentPane().add(btnNoOfGrades); 

     btnGrades = new JButton("Submit grades"); 
     btnGrades.setBounds(156, 83, 101, 20); 
     frame.getContentPane().add(btnGrades); 

     btnSort = new JButton("Sort"); 
     btnSort.setBounds(290, 61, 89, 23); 
     frame.getContentPane().add(btnSort); 

     list = new JList<Integer>(); 
     list.setBounds(60, 116, 167, 135); 
     frame.getContentPane().add(list); 
     btnNoOfGrades.addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       getNoOfGrades(); 

      } 
     }); 
     btnGrades.addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       addToList(); 

      } 
     }); 

     btnSort.addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       bubbleSort(grades); 

      } 
     }); 
    } 

    private void addToList() { 
     inputStr = inputGrades.getText().toString().replaceAll(" ", ""); 

     if (inputStr.isEmpty()) { 
      tvGrades.setText("no grades added"); 
     } else { 
      // converts string to integer and checks if item is already 
      // added 

      if (grades.size() < numOfGrades) { 

       inputGradesInt = Integer.parseInt(inputStr); 
       if (inputGradesInt < 0 || inputGradesInt > 10) { 

        tvGrades.setText("Enter a grade between 1-10"); 
       } else { 

        grades.add(inputGradesInt); 
        list.setListData(grades.toArray()); 

        inputGrades.setText(""); 
        list.notify(); 
       } 

      } else { 

       btnSort.setEnabled(true); 
      } 

     } 

    } 

    private void getNoOfGrades() { 

     inputStr = inputNoOfGrades.getText().toString();//.replaceAll(" ", ""); 

     if (inputStr.isEmpty()) { 
      tvNoOfGrades.setText("no items added"); 
     } else { 
      // converts string to integer and checks if item is already 
      // added 

      numOfGrades = Integer.parseInt(inputStr); 
      if (numOfGrades > 0) { 
       inputNoOfGrades.setEnabled(false); 
       btnNoOfGrades.setEnabled(false); 
       tvGrades.setText("Enter " + numOfGrades 
         + " student grades between 1-10"); 
      } 
     } 

    } 

    private void bubbleSort(ArrayList<Integer> grades) { 

     for (int i = grades.size() - 1; i >= 0; i--) { 
      for (int j = 0; j < i; j++) { 
       if (grades.get(j) > grades.get(j + 1)) { 
        int temp = grades.get(j); 
        grades.set(j, grades.get(j + 1)); 
        grades.set(j + 1, temp); 
       } 
      } 
     } 
    } 

} 

Answer 1

Collection.toArray()回报Object[]。您需要使用Collection.toArray(T[])，让您的特定对象类型的数组：

list.setListData(grades.toArray(new Integer[grades.size()]));