我是Java新手,需要在方法返回null和引用變量時找出過程。當方法返回null時會發生什麼
下面是該方法的代碼:
public Lot getLot(int lotNumber)
{
if((lotNumber >= 1) && (lotNumber < nextLotNumber)) {
// The number seems to be reasonable.
Lot selectedLot = lots.get(lotNumber - 1);
// Include a confidence check to be sure we have the
// right lot.
if(selectedLot.getNumber() != lotNumber) {
System.out.println("Internal error: Lot number " +
selectedLot.getNumber() +
" was returned instead of " +
lotNumber);
// Don't return an invalid lot.
selectedLot = null;
}
return selectedLot;
}
else {
System.out.println("Lot number: " + lotNumber +
" does not exist.");
return null;
}
}
當方法返回null和參考變量,而具有類數據類型會發生什麼?
請用簡單的語言解釋。
如果您不小心,最終可能會得到NPE ..:P。沒什麼特別的事返回'null'就像返回對其他實例的引用。 – TheLostMind 2014-11-03 10:32:33