java – JTextArea仅包含数字,但允许负值

DocumentFilter onlyNumberFilter = new AxisJTextFilter();
    final JTextArea areaTextoXMin = new JTextArea(String.valueOf(xMin));
    ((AbstractDocument)areaTextoXMin.getDocument()).setDocumentFilter(onlyNumberFilter);

适用于正数,但不适用于负数.我该如何解决这个问题？

编辑：对不起,AxisJTextFilter是在互联网上找到的,我忘记了.它的代码是：

import javax.swing.text.*;
import java.util.regex.*;

public class AxisJTextFilter extends DocumentFilter
{
    public void insertString(DocumentFilter.FilterBypass fb,int offset,String text,AttributeSet attr) throws BadLocationException
    {
        StringBuilder sb = new StringBuilder();
        sb.append(fb.getDocument().getText(0,fb.getDocument().getLength()));
        sb.insert(offset,text);
        if(!containsOnlyNumbers(sb.toString())) return;
        fb.insertString(offset,text,attr);
    }
    public void replace(DocumentFilter.FilterBypass fb,int length,fb.getDocument().getLength()));
        sb.replace(offset,offset + length,text);
        if(!containsOnlyNumbers(sb.toString())) return;
        fb.replace(offset,length,attr);
    }
    public boolean containsOnlyNumbers(String text)
    {
        Pattern pattern = Pattern.compile("d*(.d{0,3})?");
        Matcher matcher = pattern.matcher(text);
        boolean isMatch = matcher.matches();
        return isMatch;
    }
}