Probleme mit benutzerdefinierten verknüpften Liste zu haben und die Anwendung auf JTable

Question

Ich habe Probleme eine JTable Erstellen eines benutzerdefinierten Tabellenmodells und benutzerdefinierte verknüpfte Liste. Ich hoffe, dass es einige einfache Änderungen gibt, die ich vermisse.

Meine Hauptklasse:

import java.util.ArrayList; 
import java.util.*; 
import java.io.*; 
import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.table.*; 
public class StudentInterface { 
public static void main(String[] args){ 
     new StudentInterface(); 
    } 
    //create a linked list  
    MyLinkedList studentPack = new MyLinkedList(); 

public StudentInterface(){ 
    //create jFrame 
    JFrame jFrame = new JFrame("Student Information Interface"); 
    jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    jFrame.setSize(400,300); 
    jFrame.setVisible(true); 
    jFrame.setDefaultLookAndFeelDecorated(true); 
    jFrame.setPreferredSize(new Dimension(600, 400)); 

    //create content panes 
    JPanel headerPanel = new JPanel(); 
    JPanel tablePanel = new JPanel(); 
    JPanel buttonPanel = new JPanel(); 
    JPanel combinedPanel = new JPanel(); 
    headerPanel.setLayout(new BorderLayout()); 
    tablePanel.setLayout(new FlowLayout()); 
    buttonPanel.setLayout(new FlowLayout()); 
    combinedPanel.setLayout(new BorderLayout()); 

    //add label to header content panel 
    JLabel headerLabel1 = new JLabel("Welcome to the Student Information Interface"); 
    JLabel headerLabel2 = new JLabel("***Click a cell to edit data***"); 
    JLabel headerLabel3 = new JLabel("***Click a column header to sort***"); 
    headerLabel1.setHorizontalAlignment(JLabel.CENTER); 
    headerLabel2.setHorizontalAlignment(JLabel.CENTER); 
    headerLabel3.setHorizontalAlignment(JLabel.CENTER); 
    headerPanel.add(headerLabel1, BorderLayout.NORTH); 
    headerPanel.add(headerLabel2, BorderLayout.CENTER); 
    headerPanel.add(headerLabel3, BorderLayout.SOUTH); 

    //Where the GUI is created: 
    JMenuBar menuBar; 
    JMenu menu, submenu; 
    JMenuItem exitMenuItem; 
    JMenuItem saveMenuItem; 
    JMenuItem loadMenuItem; 

    //Create the menu bar. 
    menuBar = new JMenuBar(); 

    //Build the main menu. 
    menu = new JMenu("File"); 
    menu.setMnemonic(KeyEvent.VK_A); 
    menu.getAccessibleContext().setAccessibleDescription("The only menu in this program that has menu items"); 
    menuBar.add(menu); 

    //create menu items 
    exitMenuItem = new JMenuItem("Exit",KeyEvent.VK_T); 
    menu.add(exitMenuItem); 
    jFrame.setJMenuBar(menuBar); 

    //create table 
    tableModel model; 
    model = new tableModel(new MyLinkedList()); 
    JTable table = new JTable(model); 

    //add list to list content panel 
    JScrollPane scrollPane = new JScrollPane(table); 
    scrollPane.setPreferredSize(new Dimension(580, 400)); 
    tablePanel.add(scrollPane); 

    //add buttons to button content panel 
    JButton addButton = new JButton("Add"); 
    JButton removeButton = new JButton("Remove"); 
    buttonPanel.add(addButton); 
    buttonPanel.add(removeButton); 

    addButton.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
     //verify pack is not full 
     int packSize = studentPack.size(); 
     if (packSize >= 10) 
      { 
      JOptionPane.showMessageDialog(null, 
      "The interface is full. Please remove a student first.", 
      "Interface Full", 
      JOptionPane.WARNING_MESSAGE); 
      return; 
      } 

     JPanel p1 = new JPanel(new GridLayout(2,1)); 
     JTextField t1 = new JTextField(); 
     JLabel labell = new JLabel("Please enter the first name of the student you would like to add:"); 
     p1.add(labell); 
     p1.add(t1); 
     JOptionPane.showMessageDialog(null,p1,"First Name",JOptionPane.PLAIN_MESSAGE); 
     String userFirstName = t1.getText(); 

     JPanel p2 = new JPanel(new GridLayout(2,1)); 
     JTextField t2 = new JTextField(); 
     JLabel label2 = new JLabel("Please enter the last name of the student you would like to add:"); 
     p2.add(label2); 
     p2.add(t2); 
     JOptionPane.showMessageDialog(null,p2,"Last Name",JOptionPane.PLAIN_MESSAGE); 
     String userLastName = t2.getText(); 

     JPanel p3 = new JPanel(new GridLayout(2,1)); 
     JTextField t3 = new JTextField(); 
     JLabel label3 = new JLabel("Please enter the major of the student you would like to add:"); 
     p3.add(label3); 
     p3.add(t3); 
     JOptionPane.showMessageDialog(null,p3,"Major",JOptionPane.PLAIN_MESSAGE); 
     String userMajor = t3.getText(); 

     JPanel p4 = new JPanel(new GridLayout(2,1)); 
     JTextField t4 = new JTextField(); 
     JLabel label4 = new JLabel("Please enter the NetID of the student you would like to add:"); 
     p4.add(label4); 
     p4.add(t4); 
     JOptionPane.showMessageDialog(null,p4,"NetID",JOptionPane.PLAIN_MESSAGE); 
     String userNetID = t4.getText(); 

     JPanel p5 = new JPanel(new GridLayout(2,1)); 
     JTextField t5 = new JTextField(); 
     JLabel label5 = new JLabel("Please enter the gender of the student you would like to add:"); 
     p5.add(label5); 
     p5.add(t5); 
     JOptionPane.showMessageDialog(null,p5,"Gender",JOptionPane.PLAIN_MESSAGE); 
     String userGender = t5.getText(); 

     JPanel p6 = new JPanel(new GridLayout(2,1)); 
     JTextField t6 = new JTextField(); 
     JLabel label6 = new JLabel("Please enter the UIN of the student you would like to add:"); 
     p6.add(label6); 
     p6.add(t6); 
     JOptionPane.showMessageDialog(null,p6,"UIN",JOptionPane.PLAIN_MESSAGE); 
     String userUIN = t6.getText(); 

     JPanel p7 = new JPanel(new GridLayout(2,1)); 
     JTextField t7 = new JTextField(); 
     JLabel label7 = new JLabel("Please enter the age of the student you would like to add:"); 
     p7.add(label7); 
     p7.add(t7); 
     JOptionPane.showMessageDialog(null,p7,"Age",JOptionPane.PLAIN_MESSAGE); 
     String userAgeInput = t7.getText(); 
     int userAge = Integer.parseInt(userAgeInput); 

     JPanel p8 = new JPanel(new GridLayout(2,1)); 
     JTextField t8 = new JTextField(); 
     JLabel label8 = new JLabel("Please enter the GPA of the student you would like to add:"); 
     p8.add(label8); 
     p8.add(t8); 
     JOptionPane.showMessageDialog(null,p8,"GPA",JOptionPane.PLAIN_MESSAGE); 
     String userGPAInput = t8.getText(); 
     double userGPA = Double.parseDouble(userGPAInput); 

     //create student Student 
     Student studentStudent = new Student(userFirstName, userLastName, userMajor, userGPA, userUIN, userNetID, userAge, userGender); 

     //store Student in linked list 
     model.addStudent(studentStudent); 
     } 
    }); 

    removeButton.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
     //verify pack is not full 
     if (studentPack.size() == 0) 
      { 
      JOptionPane.showMessageDialog(null, 
      "The interface is empty. Please add a student first.", 
      "Interface Empty", 
      JOptionPane.WARNING_MESSAGE); 
      return; 
      } 

     JPanel p9 = new JPanel(new GridLayout(2,1)); 
     JTextField t9 = new JTextField(); 
     JLabel label9 = new JLabel("Please enter the first name of the student you would like to remove: **Case Sensitive**"); 
     p9.add(label9); 
     p9.add(t9); 
     JOptionPane.showMessageDialog(null,p9,"First Name",JOptionPane.PLAIN_MESSAGE); 
     String userFirstName = t9.getText(); 

     JPanel p10 = new JPanel(new GridLayout(2,1)); 
     JTextField t10 = new JTextField(); 
     JLabel label10 = new JLabel("Please enter the last name of the student you would like to remove: **Case Sensitive**"); 
     p10.add(label10); 
     p10.add(t10); 
     JOptionPane.showMessageDialog(null,p10,"First Name",JOptionPane.PLAIN_MESSAGE); 
     String userLastName = t10.getText(); 

     //remove student Student in linked list 
     } 
    }); 

    exitMenuItem.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      System.exit(0); 
     } 
    }); 

    //nest button and list panels in combined content panel 
    combinedPanel.add(headerPanel, BorderLayout.NORTH); 
    combinedPanel.add(tablePanel, BorderLayout.CENTER); 
    combinedPanel.add(buttonPanel, BorderLayout.SOUTH); 

    //add combined content panel to frame 
    jFrame.add(combinedPanel); 
    jFrame.pack(); 
    jFrame.setLocationRelativeTo(null); 

    JOptionPane.showMessageDialog(null, 
    "***Click a cell to edit data*** \n ***Click a column header to sort***", "How to edit/sort data", JOptionPane.INFORMATION_MESSAGE); 
    } 

public class tableModel extends AbstractTableModel { 

public final String[] columnNames = { "First Name", "Last Name", "Major:", "GPA", "UIN", "NetID", "Age", "Gender" }; 
private MyLinkedList data; 

public tableModel(MyLinkedList data) { 
    this.data = data; 
} 

@Override 
public int getColumnCount() { 
    return columnNames.length; 
} 

@Override 
public String getColumnName(int column) { 
    return columnNames[column]; 
} 

@Override 
public int getRowCount() { 
    return data.size(); 
} 

public void addStudent(Student student) { 
     int row = data.size(); 
     data.add(student); 
     fireTableRowsInserted(row, row); 
    } 

public void removeStudent(int i) { 
     int row = data.size(); 
     data.remove(i); 
     fireTableRowsDeleted(row, row); 
    } 

@Override 
public Student getValueAt(int rowIndex, int columnIndex) { 
    Object student = data.getNode(rowIndex); 
    if (student == null) { 
     return null; 
    } 
    switch (columnIndex) { 
    case 0: 
     return student.getFirstName(); 
    case 1: 
     return student.getLastName(); 
    case 2: 
     return student.getMajor(); 
    case 3: 
     return student.getGPA(); 
    case 4: 
     return student.getUIN(); 
    case 5: 
     return student.getNetID(); 
    case 6: 
     return student.getAge(); 
    case 7: 
     return student.getGender(); 
    default: 
     return null; 
    } 
} 
} 
} 

Hier ist meine Klasse für das Objekt Student:

public class Student { 
    // Declare attributes here 
    String firstName; 
    String lastName; 
    String major; 
    double gpa; 
    String uin; 
    String netid; 
    int age; 
    String gender; 

    public Student(String newFirstName, String newLastName, String newMajor, double newGPA, String newUIN, String newNetID, int newAge, String newGender){ 
     setFirstName(newFirstName); 
     setLastName(newLastName); 
     setMajor(newMajor); 
     setGPA(newGPA); 
     setUIN(newUIN); 
     setNetID(newNetID); 
     setAge(newAge); 
     setGender(newGender); 
    } 

    //Mutators 
    public void setFirstName(String newFirstName) { 
     firstName = newFirstName; 
    } 

    public void setLastName(String newLastName) { 
     lastName = newLastName; 
    } 

    public void setMajor(String newMajor) { 
     major = newMajor; 
    } 

    public void setGPA(double newGPA) { 
     gpa = newGPA; 
    } 

    public void setUIN(String newUIN) { 
     uin = newUIN; 
    } 

    public void setNetID(String newNetID) { 
     netid = newNetID; 
    } 

    public void setAge(int newAge) { 
     age = newAge; 
    } 

    public void setGender(String newGender) { 
     gender = newGender; 
    } 

    //Accessors 
     public String getFirstName() { 
     return firstName; 
    } 

     public String getLastName() { 
     return lastName; 
    } 

     public String getMajor() { 
     return major; 
    } 

     public double getGPA() { 
     return gpa; 
    } 

     public String getUIN() { 
     return uin; 
    } 

     public String getNetID() { 
     return netid; 
    } 

     public int getAge() { 
     return age; 
    } 

     public String getGender() { 
     return gender; 
    } 
} 

Hier ist meine überarbeitete verkettete Liste Klasse:

public class MyLinkedList<Student>{ 
    private Node<Student> lastNode; 
    private int nodeCount; 

    public MyLinkedList(){ 
     this.lastNode = null; 
     this.nodeCount = 0; 
    } 

    public int size() { 
     return nodeCount; 
    } 

    public boolean isEmpty() { 
     return this.nodeCount == 0; 
    } 

    public void add(Student student) { 
     Node<Student> currentNode = new Node<Student>(student); 
     if (this.lastNode != null) { 
      currentNode.index = lastNode.index + 1; 
      currentNode.previousNode = lastNode; 
      lastNode.nextNode = currentNode; 
     }else { 
      currentNode.previousNode = null; 
      currentNode.index = 0; 
     } 
     this.lastNode = currentNode; 
     this.nodeCount++; 
    } 

    public Student get(int index){ 
     //error handling 
     if(this.isEmpty() || index < 0 || index > this.nodeCount){ 
      return null; 
     } 
     // 
     Node<Student> currentNode; 
     int count = lastNode.index - index; 
     currentNode = lastNode; 

     while (count > 0) { 
      currentNode = currentNode.previousNode; 
      count--; 
     } 

     return currentNode.student; 
    } 

    public Node<Student> getNode(int index){ 
     //error handling 
     if(this.isEmpty() || index < 0 || index > this.nodeCount){ 
      return null; 
     } 
     // 
     int count = lastNode.index - index; 
     Node<Student> currentNode = lastNode; 

     while (count > 0){ 
      currentNode = currentNode.previousNode; 
      count--; 
     } 

     return currentNode; 
    } 

    public boolean insert(Student student, int index){ 
     Node<Student> currentNode; 

     if (this.getNode(index) != null) 
      { 
      Node<Student> newNode = new Node<Student>(student); 
      currentNode = this.getNode(index); 
      newNode.index = index; 

      if (null != currentNode.previousNode) 
       { 
       currentNode.previousNode.nextNode = newNode; 
       newNode.previousNode = currentNode.previousNode; 
       } 

      currentNode.previousNode = newNode; 
      newNode.nextNode = currentNode; 
      currentNode = newNode; 

      while (currentNode.nextNode != null) 
       { 
       currentNode = currentNode.nextNode; 
       currentNode.index++; 
       } 

       this.nodeCount++; 
       return true; 
      } 
     else 
      { 
      return false; // error handling 
      } 
    } 

    public boolean remove(int index){ 
     Node<Student> currentNode; 

     if (this.getNode(index) != null){ 
      currentNode = this.getNode(index); 

      if(currentNode.previousNode != null) { 
       currentNode.nextNode.previousNode = currentNode.previousNode; 
       currentNode.previousNode.nextNode = currentNode.nextNode; 
      } else if (currentNode.nextNode != null){ 
       currentNode.nextNode.previousNode = null; 
      } else if (this.isEmpty()){ 
       this.lastNode = null; 
      } 

      while (currentNode.nextNode != null){ 
       currentNode = currentNode.nextNode; 
       currentNode.index--; 
      } 

      this.nodeCount--; 
      return true; 
     }else { 
      return false; 
     } 
    } 

    private static class Node<Student>{ 
    public Node<Student> nextNode = null; 
    public Node<Student> previousNode = null; 
    public int index; 
    public Student student; 

    public Node(Student student){ 
     this.student = student; 
    } 
    } 
} 

Answer 1

Diese ...

public class tableModel extends AbstractTableModel { 
    //...  
    @Override 
    public Student getValueAt(int rowIndex, int columnIndex) { 
     Object student = data.getNode(rowIndex); 
     if (student == null) { 
      return null; 
     } 
     switch (columnIndex) { 
      case 0: 
       return student.getFirstName(); 
      case 1: 
       return student.getLastName(); 
      case 2: 
       return student.getMajor(); 
      case 3: 
       return student.getGPA(); 
      case 4: 
       return student.getUIN(); 
      case 5: 
       return student.getNetID(); 
      case 6: 
       return student.getAge(); 
      case 7: 
       return student.getGender(); 
      default: 
       return null; 
     } 
    } 
} 

gibt mir einen Compiler-Fehler, weil student ist ein Object und Object hat keine der Methoden, die Sie versuchen zu verwenden.

Die offensichtliche Lösung ist ... es

@Override 
public Student getValueAt(int rowIndex, int columnIndex) { 
    Student student = data.getNode(rowIndex); 

Okay, zu verwenden, sind jetzt zwei Probleme. Erste getValueAt sollte nicht Student zurückkehren, sollte es Object und zwei getNode kehrt Node<Student>

Also statt, es sollte wohl etwas mehr wie ...

@Override 
public Object getValueAt(int rowIndex, int columnIndex) { 
    Student student = data.get(rowIndex); 

Okay, aber jetzt sein, dies verursacht zurückkehren ein Compilerfehler, aber warum? get gibt eine Student zurück?

Ich verfolgt das Problem bis public class MyLinkedList<Student> { ... Stattdessen, wenn wir es public class MyLinkedList { machen, gehen alle Fehler weg.

Ihre MyLinkedList nicht wirklich benötigen die generische Signatur <Student>, wurde der Compiler sie als „generische“ Token zu sehen und wurde mit Object in Ihrem Code zu ersetzen, so dass die get Methode wurde public Object get(int index) als Instanz MyLinkedList didn‘ t bietet ein Basisobjekt, von dem aus zu starten ... ja für Generika: P

nun am Ende mit etwas, das erzeugen kann ...