public class DocDate implements Comparable<DocDate>{
 
    private Date date;
    private String numero;
 
    public String getNumero() {
        return numero;
    }
 
    public void setNumero(String numero) {
        this.numero = numero;
    }
 
     public Date getDate() {
        return date;
    }
 
    public void setDate(Date date) {
        this.date = date;
    }
 
    public int compareTo(DocDate docDate) {
        return docDate.getDate().compareTo(docDate.getDate());
    }
 
}
Collections.sort(listDocDate);
 for (Iterator it = listDocDate.iterator(); it.hasNext() {
            DocDate fact = (DocDate) it.next();
            System.out.println(fact.getDate()+" "+fact.getNumero());
  }