public class A
{
private ArrayList list = new Arraylist();
public void setArraylist(Araylist list)
{
this.list = list;
}
public Arraylist getArraylist()
{
return list;
}
}A a = new A();
a.getArraylist().add("數據");會報java.lang.NullPointerException,怎么解決啊?????????????????
{
private ArrayList list = new Arraylist();
public void setArraylist(Araylist list)
{
this.list = list;
}
public Arraylist getArraylist()
{
return list;
}
}A a = new A();
a.getArraylist().add("數據");會報java.lang.NullPointerException,怎么解決啊?????????????????
Arraylist写错了(有好几个地方),改为ArrayList
{
private ArrayList list = new ArrayList();
public void setArraylist(ArrayList list)
{
this.list = list;
}
public ArrayList getArraylist()
{
return list;
}
public static void main(String[] args){
t1 a = new t1();
a.list.add("數據");
}
}
private ArrayList list = new ArrayList();已经防止了程序员忘记初始化了public class Test {
public static void main(String[] args) {
A a = new A();
a.getArrayList().add("数据");
System.out.println(a.getArrayList().get(0));
}
}class A
{
private ArrayList list = new ArrayList();
public void setArrayList(ArrayList list)
{
this.list = list;
}
public ArrayList getArrayList()
{
return list;
}
} output:数据
如果是,你把那个修饰符private改为public
试下
{
private ArrayList list = new ArrayList();
public void setArrayList(ArrayList list)
{
this.list = list;
}
public ArrayList getArrayList()
{
return list;
}
}
换成 private static ArrayList list = new ArrayList();