how to create list of list in java ???

[ilayaraja]

i want make List to List<List<List>>


class IdentClass{

Integer testIdent;
Integer partIdent;
Integer itemIdent;

public IdentClass(Integer testIdent,Integer partIdent,Integer itemIdent){

this.testIdent = testIdent;
this.partIdent = partIdent;
this.itemIdent = itemIdent;
}

}

public class Test{
List identList = new ArrayList();
for(IdentClass i : identList)
System.out.println(i.testIdent+"\t"+i.partIdent+"\ t"+i.itemIdent);
}

my output :

//test part item
1 12 31
1 23 12
1 23 15
1 23 17
1 97 28
1 97 35
1 97 52
2 65 1
2 65 26
2 65 37
2 82 22
3 11 27
3 11 28
3 12 31
3 12 33
3 65 32
3 74 26

i have a identList which prints above output in sorted order.

but i need testList in below format :

List<List<List>> testList = new ArrayList<List<List>>();

for(List<List> partList : testList){ // for test
for(List itemList : partList){ // for part
for(IdentClass i : itemList){ // for item
System.out.println(i.testIdent+"\t"+i.partIdent+"\ t"+i.itemIdent);
}
}
}

my question is how to make this testList ??

[literallyjer]

You can't use interfaces when declaring the generic lists.

Arraylist<ArrayList<String>> listOfListOfStrings = new ArrayList<ArrayList<String>>();

or

List<ArrayList<String>> listOfListOfStrings = new ArrayList<ArrayList<String>>();

You probably could use the unknown type (?) but the deeper you dive into generics, the harder the code is to write/maintain.

http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf

EDIT: This works...

ArrayList<? extends List<?>> list = new ArrayList<ArrayList<String>>();