Question

I having a doubt regarding accessing an array of arraylist in jsp using iterator tag.

In my action class i used the following codes..,

ArrayList[] arr= new ArrayList[10]; 

for(int i = 0; i < 10; i++) { 
    arr[i] = new ArrayList<bean>();
} 

while (some conditions) { 
    arr[i].add(new bean(some values)); 
    i++; 
}

My question is.. how can i access the arr[0],arr[1]…arr[n] arraylists in iterator..?

The following code is working perfectly.., but please improve it to achieve my result..!

<s:iterator value="display.arr[0]">
  ...
</s:iterator>

Helps will be appreciated..!

Answer 1

I’m wondering if you looked at the iterator tag documention much; there are at least 3-4 ways to go about doing this, including using an immediate list of indexes, using the "begin"/"end" attributes, using "var" to hold the outer item (not strictly necessary, but IMO it’s more communicative), etc.

Assume a property named "s" in the bean class, which I call SomeBean:

<s:iterator value="displays" var="display">
  <s:iterator value="#display">
    ${s}<br/>
  </s:iterator>
</s:iterator>

Using the Java code at the bottom, this produces the following output:

Outer: 0, Inner: 0
Outer: 0, Inner: 1
Outer: 0, Inner: 2
Outer: 1, Inner: 0
Outer: 1, Inner: 1
Outer: 1, Inner: 2
Outer: 2, Inner: 0
Outer: 2, Inner: 1
Outer: 2, Inner: 2

The complete action driving this code; I just return a new list every time as an example:

public class NestedListsAction extends ActionSupport {

    public List<List<SomeBean>> getDisplays() {
        List<List<SomeBean>> displays = new ArrayList<List<SomeBean>>();

        for (int i = 0; i < 3; i++) {
            List<SomeBean> innerList = new ArrayList<SomeBean>();
            for (int j = 0; j < 3; j++) {
                innerList.add(new SomeBean(String.format("Outer: %d, Inner: %d", i, j)));
            }
            displays.add(innerList);
        }

        return displays;
    }

    private class SomeBean {
        private String s;

        public SomeBean(String s) {
            this.s = s;
        }

        public String getS() {
            return s;
        }
    }

}

Note the SO policy on accepting answers. Normally I wouldn’t bring it up to a new user, but IMO I expended more effort answering this question than you did researching it, which makes me depressed.