Jtable & queue !!

Question

Hello! I am new at using Jtable and I need some help. I want to write the following CODE to display data from queue in the table

a problem : the data does not appear in the table

i dont kow what is a problem !!

i need help , please

Source Code :

// class student

public class student {
    int id,age;
    String fn,ln;

    public student(int id,String fn,String ln,int age){
        this.age = age;
        this.id = id;
        this.fn = fn;
        this.ln = ln;
    }
}

// class node

public class node {
    student info;
    node link;
    public node(student st,node next){
        this.info = info;
        this.link = link;
    }

}

// class queue

import javax.swing.*;

public class Queue{
    node front ,rear;
    int length;

    public void enqueue( student x){
     node newnode=new node(x,null);
     if(front==null)
      front=rear=newnode;
     else{
      rear.link=newnode;
      rear=newnode;
     }length++;
    }


    public student dequeue(){
     student temp=front.info;
     if(front==null && rear==null){
      throw new RuntimeException("empty");
     }else{

      front=front.link;
      if(front==null)
      rear=null;

      length--;
     }return temp;
    }


    public String[][] getData(){
      Queue x= new Queue();
      x.front= front;
      x.rear = rear;
      String s[][] = new String[x.length][4];
     if(x.front==null){
     JOptionPane.showMessageDialog(null,"the Queue is empty,you must add new student befor"); 
     }else{

      student tmp;
      for(int i=0;i<x.length;i++){

       try{
       tmp = x.dequeue();
       s[i][0] = tmp.id + " ";
       s[i][1] = tmp.fn;
       s[i][2] = tmp.ln;
       s[i][3] = tmp.age + " ";

       }catch(Exception e){
       System.out.println("Exception from getData");
       } 
      }
     }
     return s;
    }

}

// class program

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class program extends JFrame implements ActionListener{

    Container c;

    JTextField txtID,txtFN,txtLN,txtAge;
    JLabel lblTitle,lblID,lblFN,lblLN,lblAge;
    JButton btnAdd,btnUpdate,btnDelet,btnPrint,btnSort,btnRefresh,btnCancel;
    JTable table;

    String data[][];
    Queue q;

    public program(){
     c = getContentPane();
     setTitle(" Student Applicaion ");
     c.setLayout(null);
     q = new Queue();

     // add lbl
     lblTitle =  new JLabel("ADD NEW STUDENT");
     lblTitle.setFont(new Font ("Helvetica", Font.PLAIN, 20));
     lblTitle.setBounds(50,20,200,20);
     c.add(lblTitle);


     lblID =  new JLabel("ID");
     lblID.setBounds(50,50,70,20);
     c.add(lblID);

     lblFN =  new JLabel("First Name");
     lblFN.setBounds(50,80,70,20);
     c.add(lblFN);

     lblLN =  new JLabel("Last Name");
     lblLN.setBounds(50,110,70,20);
     c.add(lblLN);

     lblAge =  new JLabel("Age");
     lblAge.setBounds(50,140,70,20);
     c.add(lblAge);

     // add txt
     txtID = new JTextField();
     txtID.setBounds(130,50,120,20);
     c.add(txtID);

     txtFN = new JTextField();
     txtFN.setBounds(130,80,120,20);
     c.add(txtFN);

     txtLN = new JTextField();
     txtLN.setBounds(130,110,120,20);
     c.add(txtLN);

     txtAge = new JTextField();
     txtAge.setBounds(130,140,120,20);
     c.add(txtAge);

     // add btn
     btnAdd = new JButton("Add");
     btnAdd.setBounds(90,180,70,25);
     c.add(btnAdd);

     btnRefresh = new JButton("Refresh");
     btnRefresh.setBounds(165,180,80,25);
     c.add(btnRefresh);



     btnUpdate = new JButton("Update");
     btnUpdate.setBounds(300,50,100,20);
     c.add(btnUpdate);

     btnDelet = new JButton("Delet");
     btnDelet.setBounds(300,80,100,20);
     c.add(btnDelet);

     btnPrint = new JButton("Print");
     btnPrint.setBounds(300,110,100,20);
     c.add(btnPrint);

     btnSort = new JButton("Sort");
     btnSort.setBounds(300,140,100,20);
     c.add(btnSort);

     btnCancel= new JButton("Cancel");
     btnCancel.setBounds(355,435,80,25);
     c.add(btnCancel);

     // add table
    // print();


     btnAdd.addActionListener(this);
     btnUpdate.addActionListener(this);
     btnDelet.addActionListener(this);
     btnPrint.addActionListener(this);
     btnSort.addActionListener(this);
     btnRefresh.addActionListener(this);
     btnCancel.addActionListener(this);

     setSize(450, 500);
     setLocationRelativeTo(null);
     setDefaultCloseOperation(EXIT_ON_CLOSE); 
     setVisible(true);
    }

      public void actionPerformed(ActionEvent e){
       if(e.getSource() == btnCancel)
        System.exit(0);
       else if(e.getSource() ==  btnRefresh){
        txtAge.setText("");
        txtFN.setText("");
        txtID.setText("");
        txtLN.setText("");
       }
       else if(e.getSource() == btnAdd){
        if(isThreeDigit(txtID.getText().trim()) == false || isNumber(txtID.getText().trim()) == false)
          JOptionPane.showMessageDialog(null,"you entered invalid ID");
        else if(isCapital(txtFN.getText().trim()) == false)
         JOptionPane.showMessageDialog(null,"you must begin First name with capital Character");
        else if(!isString(txtFN.getText().trim()) || !(isString(txtLN.getText().trim())))
         JOptionPane.showMessageDialog(null,"You can't enter number on your name");
        else if(checkAge(txtAge.getText().trim()) == false) 
         JOptionPane.showMessageDialog(null,"You must enter real age in numbers format");
        else{

         student st = new student(Integer.parseInt(txtID.getText().trim()),txtFN.getText(),
         txtLN.getText(),Integer.parseInt(txtAge.getText().trim())); 
         q.enqueue(st);


        // print();

      }
       }
       else if(e.getSource() == btnPrint){
        print();

       }

      }

      public void print(){
        String col[] = {"ID","FName","LName","Age"};
      data = q.getData();
      table = new JTable(data,col);
     // table.editingStopped(ChangeEvent e) ;
      JScrollPane scrollPane = new JScrollPane(table);
      scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
      scrollPane.setBounds(10,230,420,200);
      c.add(scrollPane);


      }
//~~~~~~~~~~~~ Constraints

    public boolean isThreeDigit(String id){
     if(id.length() <= 3)
      return true;


     return false;
    }
    public boolean checkAge(String age){

      if(!isNumber(age) || Integer.parseInt(age) > 90 || Integer.parseInt(age) < 6 )
       return false;

       return true;
    }
     public boolean isNumber(String id){

      for(int i=0;i<id.length();i++){
      char c=id.charAt(i);
      if(c>'9'|| c<'0') 
       return false; 
       }
       return true;
     }
    public boolean isString(String id){

     for(int i=0;i<id.length();i++){
      char c=id.charAt(i);
      if(c<='9'|| c<='0') 
       return false;
       }
       return true;

    }

    public boolean isCapital(String FN){
     char c=FN.charAt(0);
     if(c>='A'&& c<='Z')
     return true;

     return false;
    }


    public static void main (String[] args) {
     new program();
}
}

Answer 1

You're class queue should implement TableModel. Then create your table with:

Queue q= new Queue();
JTable table= new JTable(q);

Answer 2

Two things:

1. Please use an uppercase letter to start your class names

2. A custom TableModel is probably a good idea. Instead of implementing TableModel from scratch, extend AbstractTableModel instead, since it handles all the events and listener aspects and will save you a lot of time.

Answer 3

thanx i understanded your idea i tried do this .. but i can't !! please , if you have time , do this for me .. help me please

Answer 4

I found at least one error, not sure if the only one:

public class node {
    student info;
    node link;
    public node(student st,node next){
        this.info = info;
        this.link = link;
    }
  }

this.info = info; is doing nothing at all, try this:

public class node {
    student info;
    node link;
    public node(student st,node next){
        this.info = st;
        this.link = next;
    }
}

Some unit tests would be great to catch this... or just use the collections from Java...

EDIT:
second, in getData:

        public String[][] getData(){
            Queue x= new Queue();
            x.front= front;
            x.rear = rear;
            String s[][] = new String[x.length][4];
...
            student tmp;
            for(int i=0;i<x.length;i++){

                    try{
                    tmp = x.dequeue();

you are not doing a real copy of x here:
- x.length is still zero
- you are still using the original nodes, not a copy. If you do x.dequeue() the original nodes get changed
- x.dequeue changes x.length so your loop will stop halfway

Better just navigate the queue:

public String[][] getData(){
    String s[][] = new String[length][4];
    if (front == null) {
        JOptionPane.showMessageDialog(null,"the Queue is empty,you must add new student befor");        
    } else {
        int i = 0;
        // node node = front;    // that's why class name should be uppercase!!
        node aNode = front;
        while (aNode != null) {   // for would also do...
            student tmp = aNode.info;
            s[i][0] = String.valueOf(tmp.id);  //  + " ";
            s[i][1] = tmp.fn;
            s[i][2] = tmp.ln;
            s[i][3] = String.valueOf(tmp.age);  //  + "";
            i += 1;
            aNode = aNode.link;
        }
    }
    return s;
}

EDIT2:
That way the table only will be updated when pressing the button...
Use a TableModel, as sugested in the other answers to have it updated every time the queue gets changed.
I also don't like the ideia of creating a new JTable and JScrollPane every time to update the data... I prefer to create the GUI with one instance of the JTable and just update that instance's model when needed. (The TableModel would do that for you).