Create Swing CustomLineBorder (apply by specifying top, left, bottom, right)

Overriding border to apply border only to the specified side

package test.swing;

import javax.swing.*;
import javax.swing.border.AbstractBorder;
import java.awt.*;

// Custom Line border
public class MainTest {
    public static void main(String[] args) {
        MainUI mainUI = new MainUI();
        mainUI.setVisible(true);
    }
}

class CustomLineBorder extends AbstractBorder
{
    public static final int TOP = 0x1;
    public static final int LEFT = 0x2;
    public static final int BOTTOM = 0x4;
    public static final int RIGHT = 0x8;
    private Color mColor;
    private int mThickness;
    private int mTarget;

    public CustomLineBorder(Color colour, int thickness, int target)
    {
        mColor = colour;
        mThickness = thickness;
        mTarget = target;
    }

    @Override
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height)
    {
        if (g != null)
        {
            g.setColor(mColor);
            if ((mTarget & TOP) != 0) {
                for (int i = 0; i < mThickness; i++) {
                    g.drawLine(x, y + i, width, y + i);
                }
            }
            if ((mTarget & LEFT) != 0) {
                for (int i = 0; i < mThickness; i++) {
                    g.drawLine(x + i, y, x + i, height);
                }
            }
            if ((mTarget & BOTTOM) != 0) {
                for (int i = 0; i < mThickness; i++) {
                    g.drawLine(x, height - i - 1, width, height - i - 1);
                }
            }
            if ((mTarget & RIGHT) != 0) {
                for (int i = 0; i < mThickness; i++) {
                    g.drawLine(width - i - 1, y, width - i - 1, height);
                }
            }
        }
    }

    @Override
    public Insets getBorderInsets(Component c)
    {
        return (getBorderInsets(c, new Insets(0, 0, 0, 0)));
    }

    @Override
    public Insets getBorderInsets(Component c, Insets insets)
    {
        insets.top = 0;
        insets.left = 0;
        insets.bottom = 0;
        insets.right = 0;
        if ((mTarget & TOP) != 0) {
            insets.top = mThickness;
        }
        if ((mTarget & LEFT) != 0) {
            insets.left = mThickness;
        }
        if ((mTarget & BOTTOM) != 0) {
            insets.bottom = mThickness;
        }
        if ((mTarget & RIGHT) != 0) {
            insets.right = mThickness;
        }

        return insets;
    }

    @Override
    public boolean isBorderOpaque()
    {
        return true;
    }
}

class MainUI extends JFrame {
    MainUI() {
        setPreferredSize(new Dimension(400, 420));
        
        JPanel pane = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 20));
        pane.setBackground(new Color(0x85, 0x85, 0x85));

        JLabel label = new JLabel("Red, 1, TOP");
        label.setPreferredSize(new Dimension(300, 40));
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(new CustomLineBorder(Color.RED, 1, CustomLineBorder.TOP));
        pane.add(label);

        label = new JLabel("Red, 5, LEFT");
        label.setPreferredSize(new Dimension(300, 40));
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(new CustomLineBorder(Color.RED, 5, CustomLineBorder.LEFT));
        pane.add(label);

        label = new JLabel("Red, 5, Bottom");
        label.setPreferredSize(new Dimension(300, 40));
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(new CustomLineBorder(Color.RED, 5, CustomLineBorder.BOTTOM));
        pane.add(label);

        label = new JLabel("Red, 15, Right");
        label.setPreferredSize(new Dimension(300, 40));
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(new CustomLineBorder(Color.RED, 15, CustomLineBorder.RIGHT));
        pane.add(label);

        label = new JLabel("Blue, 5, TOP LEFT");
        label.setPreferredSize(new Dimension(300, 40));
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(new CustomLineBorder(Color.BLUE, 5, CustomLineBorder.LEFT | CustomLineBorder.TOP));
        pane.add(label);

        label = new JLabel("Blue, 5, TOP RIGHT BOTTOM");
        label.setPreferredSize(new Dimension(300, 40));
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(new CustomLineBorder(Color.BLUE, 5, CustomLineBorder.TOP | CustomLineBorder.RIGHT | CustomLineBorder.BOTTOM));
        pane.add(label);

        add(pane);

        pack();
    }
}

Run