how to search an element in a JTable java?

You probably want to use a RowFilter to filter the search results. Below is an example using a RowFilter and a DocumentListener. When the user types, the rows are filter dynamically.

See RowFilter api and DocumentListener api. If you don’t like the dynamic filtering, you could just stick with the button, or you can add an ActionListener to the the JTextField, so when Enter is pressed, the filter will process. The code you would put in the listener call back (actionPerformed) would just be

  String text = jtfFilter.getText();
  if (text.trim().length() == 0) {
     rowSorter.setRowFilter(null);
  } else {
     rowSorter.setRowFilter(RowFilter.regexFilter("(?i)" + text));
  }

import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.RowFilter;
import javax.swing.SwingUtilities;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;
import javax.swing.table.TableRowSorter;

public class TestTableSortFilter extends JPanel {

    private String[] columnNames
            = {"Country", "Capital", "Population in Millions", "Democracy"};

    private Object[][] data = {
        {"USA", "Washington DC", 280, true},
        {"Canada", "Ottawa", 32, true},
        {"United Kingdom", "London", 60, true},
        {"Germany", "Berlin", 83, true},
        {"France", "Paris", 60, true},
        {"Norway", "Oslo", 4.5, true},
        {"India", "New Delhi", 1046, true}
    };

    private DefaultTableModel model = new DefaultTableModel(data, columnNames);
    private JTable jTable = new JTable(model);

    private TableRowSorter<TableModel> rowSorter
            = new TableRowSorter<>(jTable.getModel());

    private JTextField jtfFilter = new JTextField();
    private JButton jbtFilter = new JButton("Filter");

    public TestTableSortFilter() {
        jTable.setRowSorter(rowSorter);

        JPanel panel = new JPanel(new BorderLayout());
        panel.add(new JLabel("Specify a word to match:"),
                BorderLayout.WEST);
        panel.add(jtfFilter, BorderLayout.CENTER);

        setLayout(new BorderLayout());
        add(panel, BorderLayout.SOUTH);
        add(new JScrollPane(jTable), BorderLayout.CENTER);

        jtfFilter.getDocument().addDocumentListener(new DocumentListener(){

            @Override
            public void insertUpdate(DocumentEvent e) {
                String text = jtfFilter.getText();

                if (text.trim().length() == 0) {
                    rowSorter.setRowFilter(null);
                } else {
                    rowSorter.setRowFilter(RowFilter.regexFilter("(?i)" + text));
                }
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                String text = jtfFilter.getText();

                if (text.trim().length() == 0) {
                    rowSorter.setRowFilter(null);
                } else {
                    rowSorter.setRowFilter(RowFilter.regexFilter("(?i)" + text));
                }
            }

            @Override
            public void changedUpdate(DocumentEvent e) {
                throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
            }

        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable(){
            public void run() {
               JFrame frame = new JFrame("Row Filter");
               frame.add(new TestTableSortFilter());
               frame.pack();
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               frame.setLocationRelativeTo(null);
               frame.setVisible(true);
            }

        });
    }
}