我有一個類具有一個ArrayList屬性,並且具有該類的2D陣列另一個類:2D陣列
public class someThingsList {
private List<someThings> lst;
public someThingsList() {
this.lst = new ArrayList<someThings>();
}
public addThing(someThings) {
someThings s = someThings;
this.lst.add(s);
}
}
和
public class x implements y {
private static someThingsList[][] field;
public x(int h, int w) {
x.field = new someThingsList[h][w];
for (someThingsList[] lst1 : x.field)
for (someThingsList lst2 : lst1)
lst2 = new someThingsList();
}
,當我有例如用(2,2)爲H和W新的X對象,並嘗試做
x.fields[0][0].addThing(thing);
我得到一個NullPointerException錯誤,任何想法,爲什麼?
不相關,但嘗試命名您的類(和接口)與領先的大寫字母和您的變量與領先的小寫。會使代碼像「someThings s = someThings;」更具可讀性。 – sbk 2013-02-14 17:08:53
哎呀抱歉,應該是 public addThing(someThings sT)someThings s = sT; this.lst.add(s); } – codeoverflow 2013-02-14 17:17:44