private final Date theDate;

public MaClasse(Date theDate) {
  this.theDate = theDate;
}

@Override
public String toString() {
  return theDate.toString();
}

Date d = new Date();
MaClasse c = new MaClasse(d);
d.setYear(98);
System.out.println(c);

private final Date theDate;

public MaClasse(Date theDate) {
  this.theDate = (Date) theDate.clone();
}

public Date getDate() {
  return (Date) theDate.clone();
}

private final Date startDate;
private final Date endDate;

public MaClasse(Date startDate, Date endDate) {
  if (startDate.compareTo(endDate) > 0) {
    throw new IllegalArgumentException("The start date is not <= the end date.");
  }

  this.startDate = (Date) startDate.clone();
  this.endDate = (Date) endDate.clone();
}

private final Date startDate;
private final Date endDate;

public MaClasse(Date startDate, Date endDate) {
  Date copyStart = (Date) startDate.clone();
  Date copyEnd = (Date) endDate.clone()

  if (copyStart.compareTo(copyEnd) > 0) {
    throw new IllegalArgumentException("The start date is not <= the end date.");
  }

  this.startDate = copyStart;
  this.endDate = copyEnd;
}