Question

I have a function which gets a key from the user and generates a Hashtable (on a pattern specified by the key). After creating a Hashtable, I would like to populate a JTable so that each each column represents a key and every rows represents the values associated with the key. I tried everything but couldn’t get this work. I’m not creating the table from within the constructor as I need to get input from the user.

Answer 1

See How to Use Tables: Creating a Table Model.

The JTable constructor used by SimpleTableDemo creates its table model with code like this:

new AbstractTableModel() {     public String getColumnName(int col) {         return columnNames[col].toString();     }     public int getRowCount() { return rowData.length; }     public int getColumnCount() { return columnNames.length; }     public Object getValueAt(int row, int col) {         return rowData[row][col];     }     public boolean isCellEditable(int row, int col)         { return true; }     public void setValueAt(Object value, int row, int col) {         rowData[row][col] = value;         fireTableCellUpdated(row, col);     } } 

You basically have to wrap your hashtable in the above manner. Here’s an example.

package eed3si9n.hashtabletable;  import java.awt.BorderLayout; import java.util.Enumeration; import java.util.Hashtable;  import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.table.AbstractTableModel; import javax.swing.JButton; import java.awt.Dimension;  public class MainForm extends JFrame {      private static final long serialVersionUID = 1L;     private JPanel jContentPane = null;  //  @jve:decl-index=0:visual-constraint='23,38'     private JScrollPane m_scrollPane = null;     private JTable m_table = null;     private Hashtable<String, String> m_hash = null;     private JButton m_btnAdd = null;          /**      * This is the default constructor      */     public MainForm() {         super();         initialize();         m_hash = new Hashtable<String, String>();         m_hash.put('Dog', 'Bow');     }      private void onButtonPressed() {         m_hash.put('Cow', 'Moo');         m_table.revalidate();     }      /**      * This method initializes this      *       * @return void      */     private void initialize() {         this.setSize(409, 290);         this.setTitle('JFrame');         this.setContentPane(getJContentPane());     }      /**      * This method initializes jContentPane      *       * @return javax.swing.JPanel      */     private JPanel getJContentPane() {         if (jContentPane == null) {             jContentPane = new JPanel();             jContentPane.setLayout(new BorderLayout());             jContentPane.setSize(new Dimension(500, 500));             jContentPane.setPreferredSize(new Dimension(500, 500));             jContentPane.add(getM_scrollPane(), BorderLayout.NORTH);             jContentPane.add(getM_btnAdd(), BorderLayout.SOUTH);         }         return jContentPane;     }      /**      * This method initializes m_scrollPane       *        * @return javax.swing.JScrollPane        */     private JScrollPane getM_scrollPane() {         if (m_scrollPane == null) {             m_scrollPane = new JScrollPane();             m_scrollPane.setViewportView(getM_table());         }         return m_scrollPane;     }      /**      * This method initializes m_table        *        * @return javax.swing.JTable         */     private JTable getM_table() {         if (m_table == null) {             m_table = new JTable();             m_table.setModel(new AbstractTableModel(){     private static final long serialVersionUID = 1L;      public int getColumnCount() {         return 2;     }      public int getRowCount() {         return m_hash.size();     }      public String getColumnName(int column) {         if (column == 0) {             return 'Animal';         } else {             return 'Sound';         }     }      public Object getValueAt(int rowIndex, int columnIndex) {         if (columnIndex == 0) {             return getKey(rowIndex);         } else {             return m_hash.get(getKey(rowIndex));         } // if-else      }      private String getKey(int a_index) {         String retval = '';         Enumeration<String> e = m_hash.keys();         for (int i = 0; i < a_index + 1; i++) {             retval = e.nextElement();         } // for          return retval;     }              });         }         return m_table;     }      /**      * This method initializes m_btnAdd       *        * @return javax.swing.JButton        */     private JButton getM_btnAdd() {         if (m_btnAdd == null) {             m_btnAdd = new JButton();             m_btnAdd.setPreferredSize(new Dimension(34, 30));             m_btnAdd.addActionListener(new java.awt.event.ActionListener() {                 public void actionPerformed(java.awt.event.ActionEvent e) {                     onButtonPressed();                 }             });         }         return m_btnAdd;     }      public static void main(String[] args) {         //Schedule a job for the event-dispatching thread:         //creating and showing this application's GUI.         javax.swing.SwingUtilities.invokeLater(new Runnable() {             public void run() {                 MainForm frame = new MainForm();                 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);                 frame.setSize(500, 500);                 frame.setVisible(true);             }         });     } }  //  @jve:decl-index=0:visual-constraint='10,10'