java中如何实现表格的多表头显示

答案：  
首先声明，这些内容都是借鉴来的，稍微改动了一下。
主要就是三个应用类ColumnGroup， GroupableTableHeader，GroupableTableHeaderU
和一个示例类GroupableHeaderExample
1、ColumnGroup类主要负责多表头的构建
import java.awt.Component;
import java.awt.Dimension;
import java.util.Enumeration;
import java.util.Vector;
import javax.swing.JLabel;
import javax.swing.JTable;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumn;
public class ColumnGroup {
    protected TableCellRenderer renderer;
    protected Vector v;
    protected String text;
    protected int margin = 0;
    public ColumnGroup(String text) {
        this(null, text);
    }
    public ColumnGroup(TableCellRenderer renderer, String text) {
        if (renderer == null) {
            this.renderer = new DefaultTableCellRenderer() {
                public Component getTableCellRendererComponent(JTable table,
                        Object value, boolean isSelected, boolean hasFocus,
                        int row, int column) {
                    JTableHeader header = table.getTableHeader();
                    if (header != null) {
                        setForeground(header.getForeground());
                        setBackground(header.getBackground());
                        setFont(header.getFont());
                    }
                    setHorizontalAlignment(JLabel.CENTER);
                    this.setText((value == null) ? "" : value.toString());
                    setBorder(UIManager.getBorder("TableHeader.cellBorder"));
                    return this;
                }
            };
        } else {
            this.renderer = renderer;
        }
        this.text = text;
        v = new Vector();
    }
    /**
     * @param obj
     *            TableColumn or ColumnGroup
     */
    public void add(Object obj) {
        if (obj == null) {
            return;
        }
        v.addElement(obj);
    }
    /**
     * @param c
     *            TableColumn
     * @param v
     *            ColumnGroups
     */
    public Vector getColumnGroups(TableColumn c, Vector g) {
        g.addElement(this);
        if (v.contains(c))
            return g;
        Enumeration enumeration = v.elements();
        while (enumeration.hasMoreElements()) {
            Object obj = enumeration.nextElement();
            if (obj instanceof ColumnGroup) {
                Vector groups = (Vector) ((ColumnGroup) obj).getColumnGroups(c,
                        (Vector) g.clone());
                if (groups != null)
                    return groups;
            }
        }
        return null;
    }
    public TableCellRenderer getHeaderRenderer() {
        return renderer;
    }
    public Object getHeaderValue() {
        return text;
    }
    public int getSize() {
        return v == null ? 0 : v.size();
    }
    public Dimension getSize(JTable table) {
        Component comp = renderer.getTableCellRendererComponent(table,
                getHeaderValue(), false, false, -1, -1);
        int height = comp.getPreferredSize().height;
        int width = 0;
        Enumeration enumeration = v.elements();
        while (enumeration.hasMoreElements()) {
            Object obj = enumeration.nextElement();
            if (obj instanceof TableColumn) {
                TableColumn aColumn = (TableColumn) obj;
                width += aColumn.getWidth();
                width += margin;
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