Set size of JTable in JScrollPane and in JPanel with the size of the JFrame

Question

I want the table with the same width as the frame and also when I resize the frame the table need to be resized too. I think setSize() of JTable doesn't work correctly. Can you help me?

import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingUtilities;

public class Main extends JFrame {

    public Main() {
        setSize(400, 600);
        String[] columnNames = {"A", "B", "C"};
        Object[][] data = {
            {"Moni", "adsad", 2},
            {"Jhon", "ewrewr", 4},
            {"Max", "zxczxc", 6}
        };

        JTable table = new JTable(data, columnNames);
        JScrollPane tableSP = new JScrollPane(table);

        int A = this.getWidth();
        int B = this.getHeight();

        table.setSize(A, B);
        JPanel tablePanel = new JPanel();
        tablePanel.add(tableSP);
        tablePanel.setBackground(Color.red);

        add(tablePanel);
        setTitle("Marks");

        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                Main ex = new Main();
                ex.setVisible(true);
            }
        });
    }
}

Answer 1

have look at

table.setPreferredScrollableViewportSize(table.getPreferredSize());
table.setFillsViewportHeight(true);

for the code you posted here

Answer 2

Get rid of all the setSize calls. Then get rid of the tablePanel and just at the tableSP directly to the content pane of the JFrame.

The content pane of a JFrame has by default a BorderLayout, and adding a component to the BorderLayout#CENTER (which is the default when you simply use add without constraints) will make sure the component takes the size of the parent container.

Quickly adjusted your code

public class Main extends JFrame {

    public Main() {
        String[] columnNames = {"A", "B", "C"};
        Object[][] data = {
            {"Moni", "adsad", 2},
            {"Jhon", "ewrewr", 4},
            {"Max", "zxczxc", 6}
        };

        JTable table = new JTable(data, columnNames);
        JScrollPane tableSP = new JScrollPane(table);
        tableSP.setPreferredSize( 400, 600 );

        add(tableSP);
        setTitle("Marks");

        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                Main ex = new Main();
                ex.setVisible(true);
            }
        });
    }
}

Small side-note: there is no reason to extend JFrame. Just use one

Answer 3

As an alternative, use GridLayout for your tablePanel and pack() the enclosing Window.

import java.awt.Color;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingUtilities;

public class Main extends JFrame {

    public Main() {
        String[] columnNames = {"A", "B", "C"};
        Object[][] data = {
            {"Moni", "adsad", 2},
            {"Jhon", "ewrewr", 4},
            {"Max", "zxczxc", 6}
        };

        JTable table = new JTable(data, columnNames);
        JScrollPane tableSP = new JScrollPane(table);

        int A = this.getWidth();
        int B = this.getHeight();

        table.setSize(A, B);
        JPanel tablePanel = new JPanel(new GridLayout());
        tablePanel.add(tableSP);
        tablePanel.setBackground(Color.red);

        add(tablePanel);
        setTitle("Marks");

        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                Main ex = new Main();
                ex.setVisible(true);
            }
        });
    }
}