What is the difference between x_axis and line_axis of boxlayout in java?

Question

Both x_axis and line_axis arranges components from left to right. Then what's the difference between them?

This question is from Java Swing boxlayout layout manager.

Answer 1

From the official documentation:

X_AXIS - Components are laid out horizontally from left to right.

LINE_AXIS - Components are laid out the way words are laid out in a line, based on the container's ComponentOrientation property. If the container's ComponentOrientation is horizontal then components are laid out horizontally, otherwise they are laid out vertically. For horizontal orientations, if the container's ComponentOrientation is left to right then components are laid out left to right, otherwise they are laid out right to left. For vertical orientations components are always laid out from top to bottom.

Answer 2

I hope the following code example, might be able to provide more insight into what the Java Docs has to say on BoxLayout.LINE_AXIS :

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LINE_AXIS - Components are laid out the way words are laid out in a line, based on the container's ComponentOrientation property. If the container's ComponentOrientation is horizontal then components are laid out horizontally, otherwise they are laid out vertically. For horizontal orientations, if the container's ComponentOrientation is left to right then components are laid out left to right, otherwise they are laid out right to left. For vertical orientations components are always laid out from top to bottom.

---

X_AXIS - Components are laid out horizontally from left to right.

---

Do watch the last two rows, how Buttons are added to the second last JPanel from RIGHT tO LEFT and from __LEFT to RIGHT_ to the last JPanel

import java.awt.*;
import java.util.Locale;
import javax.swing.*;

public class BoxLayoutExample
{
    private JPanel topPanel;
    private JPanel middlePanel;
    private JPanel bottomPanel;
    private JPanel addedBottomPanel;
    private JButton[] button;

    public BoxLayoutExample()
    {
        button = new JButton[12];
    }

    private void displayGUI()
    {
        JFrame frame = new JFrame("Box Layout Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new GridLayout(4, 1, 5, 5));

        topPanel = new JPanel();
        topPanel.setLayout(new BoxLayout(
                            topPanel, BoxLayout.X_AXIS));
        for (int i = 0; i < 3; i++)
        {
            button[i] = new JButton(Integer.toString(i));
            topPanel.add(button[i]);
        }

        middlePanel = new JPanel();
        middlePanel.setLayout(new BoxLayout(
                            middlePanel, BoxLayout.LINE_AXIS));
        for (int i = 3; i < 6; i++)
        {
            button[i] = new JButton(Integer.toString(i));
            middlePanel.add(button[i]);
        }

        bottomPanel = new JPanel();     
        bottomPanel.setComponentOrientation(
                        ComponentOrientation.RIGHT_TO_LEFT);        
        bottomPanel.setLayout(new BoxLayout(
                            bottomPanel, BoxLayout.LINE_AXIS));
        for (int i = 6; i < 9; i++)
        {
            button[i] = new JButton(Integer.toString(i));
            bottomPanel.add(button[i]);
        }

        addedBottomPanel = new JPanel();        
        addedBottomPanel.setComponentOrientation(
                        ComponentOrientation.RIGHT_TO_LEFT);        
        addedBottomPanel.setLayout(new BoxLayout(
                            addedBottomPanel, BoxLayout.X_AXIS));
        for (int i = 9; i < 12; i++)
        {
            button[i] = new JButton(Integer.toString(i));
            addedBottomPanel.add(button[i]);
        }

        contentPane.add(topPanel);
        contentPane.add(middlePanel);
        contentPane.add(bottomPanel);
        contentPane.add(addedBottomPanel);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        Runnable runnable = new Runnable()
        {
            @Override
            public void run()
            {
                new BoxLayoutExample().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

OUTPUT :

Answer 3

X_AXIS is always horizontal. LINE_AXIS can be both based on the container's ComponentOrientation property.

Source:

https://docs.oracle.com/en/java/javase/15/docs/api/java.desktop/javax/swing/BoxLayout.html