■Tip For more notes on immutability for objects, consult Joshua Bloch’s excellent book Effective Java
Programming Language Guide(Addison-Wesley Professional, 2001). See Item 13, “Favor immutability.”
Listing 4-2.SpecialDeal Class
public class SpecialDeal {
private Airport departFrom;
private Airport arriveAt;
private BigDecimal cost;
private Date beginOn;
private Date endOn;public SpecialDeal(Airport arriveAt, Airport departFrom, BigDecimal cost,
Date beginOn, Date endOn) {
this.arriveAt = arriveAt;
this.departFrom = departFrom;
this.cost = cost;
this.beginOn = new Date(beginOn.getTime());
this.endOn = new Date(endOn.getTime());
}public BigDecimal getCost() {
return cost;
}public Airport getDepartFrom() {
return departFrom;
}public Airport getArriveAt() {
return arriveAt;
}public boolean isValidNow() {
return isValidOn(new Date());
}public boolean isValidOn(Date date) {
Assert.notNull(date, "Date must not be null");
Date dateCopy = new Date(date.getTime());
return ((dateCopy.equals(beginOn) || dateCopy.after(beginOn)) &&
(dateCopy.equals(endOn) || dateCopy.before(endOn)));
}}
CHAPTER 4 ■JUMP INTO SPRING MVC 43