我正在嘗試從csv文件中獲取特定數據。在本例中，im 使用 ID，這是文件中的第一個字符串。動物詳情.txt0,2,AmercianShorthair,100,AmercianShorthair,AmercianShorthair,y,y,900.0,Ann,3,4,GermanShepherd,100,GermanShepherd,GermanShepherd,no,yes,600.0,Dave,6,3,Poodle,100,Poodle,Poodle,yes,no,300.0,Dianna,456,4,Azawakh,50,Unknown,Azawakh,no,no,300.0,April,25041019042018,1,Vizsla,50,Vizsla,TreeingTennesseeBrindle,no,yes,500.0,Lex,3271,1,Beagle,50,Beagle,Unknown,no,no,200.0,Blanton,48331827032019,33,sheperd,50,50,50,no,yes,300.0,Mike,主應用public class AppTest {    public static void main(String[] ages) {        //Load file         AnimalManager aMgr = new AnimalManager();        aMgr.loadFromFile("AnimalDetails.txt");             //Test DELETE By Animal ID        try {        Animals anim = aMgr.getAnimalById("0");//Insert animal ID here        aMgr.deleteAnimal(anim);        } catch (IllegalArgumentException exc) {          System.out.println(exc);        }    }}經理//Delete animalpublic void deleteAnimal (Animals a) {    if (a == null)        throw new IllegalArgumentException("Animal argument is null");    animalList.remove(a);}//Get animal by IDpublic Animals getAnimalById(String ID) {    for (Animals a : this.animalList) {        if (a.getID().equals(ID))            return null;         }    return null;}當我在主應用程序中插入動物ID時，它會返回空值，而不是成功的刪除消息。這里可能有什么問題？輸出： java.lang.非法參數異常： 動物參數為空