Java wrap layout (to swing library)

WrapLayout.java

import java.awt.*;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;

public class WrapLayout extends FlowLayout
{
  private Dimension preferredLayoutSize;

	public WrapLayout()
	{
		super();
	}

	public WrapLayout(int align)
	{
		super(align);
	}

	public WrapLayout(int align, int hgap, int vgap)
	{
		super(align, hgap, vgap);
	}

	@Override
	public Dimension preferredLayoutSize(Container target)
	{
		return layoutSize(target, true);
	}

	@Override
	public Dimension minimumLayoutSize(Container target)
	{
		Dimension minimum = layoutSize(target, false);
		minimum.width -= (getHgap() + 1);
		return minimum;
	}

	private Dimension layoutSize(Container target, boolean preferred)
	{
	synchronized (target.getTreeLock())
	{
		int targetWidth = target.getSize().width;

		if (targetWidth == 0)
			targetWidth = Integer.MAX_VALUE;

		int hgap = getHgap();
		int vgap = getVgap();
		Insets insets = target.getInsets();
		int horizontalInsetsAndGap = insets.left + insets.right + (hgap * 2);
		int maxWidth = targetWidth - horizontalInsetsAndGap;

		Dimension dim = new Dimension(0, 0);
		int rowWidth = 0;
		int rowHeight = 0;

		int nmembers = target.getComponentCount();

		for (int i = 0; i < nmembers; i++)
		{
			Component m = target.getComponent(i);

			if (m.isVisible())
			{
				Dimension d = preferred ? m.getPreferredSize() : m.getMinimumSize();

				if (rowWidth + d.width > maxWidth)
				{
					addRow(dim, rowWidth, rowHeight);
					rowWidth = 0;
					rowHeight = 0;
				}

				if (rowWidth != 0)
				{
					rowWidth += hgap;
				}

				rowWidth += d.width;
				rowHeight = Math.max(rowHeight, d.height);
			}
		}

		addRow(dim, rowWidth, rowHeight);

		dim.width += horizontalInsetsAndGap;
		dim.height += insets.top + insets.bottom + vgap * 2;

		Container scrollPane = SwingUtilities.getAncestorOfClass(JScrollPane.class, target);
		if (scrollPane != null)
		{
			dim.width -= (hgap + 1);
		}

		return dim;
	}
	}

	private void addRow(Dimension dim, int rowWidth, int rowHeight)
	{
		dim.width = Math.max(dim.width, rowWidth);

		if (dim.height > 0)
		{
			dim.height += getVgap();
		}

		dim.height += rowHeight;
	}
}

Source: https://tips4java.wordpress.com/2008/11/06/wrap-layout/