Question

I have a class and this class has one public element ArrayList myList.(I have other elements too in my class but they have nothing to do with this element)

What I am trying to do is having different ArrayLists for different Class Objects. However when I tried to code this, even if I use different class objects, the code reserves every entry in one single ArrayList. What am i doing wrong?

This is what i tried:
My class:

public class myClass {

public static ArrayList myList;
public static ArrayList getList() {
    return myList;
}
public static void setList(ArrayList myList) {
    myClass.myList = myList;
}

In main:

 myClass my = new myClass();
 myClass my2 = new myClass();
 ArrayList tmp = new ArrayList();
 ArrayList tmp2 = new ArrayList();
 tmp.add("aaaaa");
 tmp.add("bbbbb");
 tmp2.add("ccccc");
 tmp2.add("ddddd");
 my.setList(tmp);
 my2.setList(tmp2);
 for(int i=0;i<my.getList().size();i++)
 {
 System.out.println(my.getList().get(i));
 }

And the output of this main is being:

ccccc
ddddd

but i want it to be:

aaaaa
bbbbb

What am i doing wrong?

Answer 1

You declared myClass#myList static, which means only one instance of myList will exist, inside the CLASS myClass. Declare it non-static, including the getter and setter, to have different instances for my and my2 and you’re good to go.