Question

Okay, I have had a question, my code has seemed to work, but I have not tested it particuarly well.

I’m trying to set an element in an ArrayList.

ArrayList<StringBuilder> g=new ArrayList<StringBuilder>();
//set the array contents
g.get(2).append("Something");

I know that doing something like

StringBuilder q=g.get(2);
q.append("something else?");
g.set(2,q);

works, and is probably the right way to do it, but it seems like such long way of doing it.

Am I doing this right, if I’m not, then is the second way I’ve mentioned the only way?

Answer 1

If you have a list of StringBuilder, which are modified in place, then the first method is fine. If you have a list of some immutable type (like String), then since you cannot change the object that you get out, you have to use a variant of the second method, because the result is not the same object.

e.g.

List<StringBuilder> widgets = new ArrayList<StringBuilder>();
// ...
StringBuilder widget = widgets.get(0);
widget.append(" version 2");

vs

List<String> widgets = new ArrayList<String>();
// ...
String widget = widgets.get(0);
widgets.set(2, widget + " version 2");