Re: Help on java generics

From:
Donkey Hot <spam@plc.is-a-geek.com>
Newsgroups:
comp.lang.java.programmer
Date:
06 Jun 2008 21:26:24 GMT
Message-ID:
<Xns9AB647A18320SH15SGybs1ysmajw54s5@194.100.2.89>
Donkey Hot <spam@plc.is-a-geek.com> wrote in
news:Xns9AB63E015976SH15SGybs1ysmajw54s5@194.100.2.89:

cidsaril@gmail.com wrote in news:67e0720b-9863-4b69-b820-f2d8a8608da3
@h1g2000prh.googlegroups.com:

I am new to Java 5 Programming and I am facing an issue with Generics
as below

In my java application , My main class is as below (I have replicated
the original scenario in the test program here )

import java.util.ArrayList;

public class TestGeneric {
     public static void main(String args[]) {

          ArrayList al = new ArrayList ();
          TestClass tc = new TestClass();
          al = tc.getList();
          System.out.println(al);

     }
}

And the TestClass is as below

import java.util.ArrayList;

public class TestClass {

     public ArrayList getList() {

          ArrayList list1 = new ArrayList();
          list1.add("Hello1");
          list1.add("Hellow1");
          ArrayList list2 = new ArrayList ();
          list2.add("Hello2");
          list2.add("Hellow2");
          ArrayList list3 = new ArrayList ();

          list3.add(list1);
          list3.add(list2);
          return list3;

     }

}

The method getList in TestClass returns as ArrayList of ArrayLists .
If I need to implement the above two class using Generics , how Can I
go about it .

Will it be ArrayList <ArrayList > al = new ArrayList <ArrayList>
(); in the main program ? or
 ArrayList <Object > al = new ArrayList <Object> ();
Please help

Thanks
Sam


ArrayList<ArrayList<String>>


Actually:

List<List<String>> al = new List<List<String>>() ;

ArrayList is the implementation, but you could use the interface List in
the variable declaration.

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