type casting

[alvations]

ArrayList<String> test = new ArrayList<String> ();
List<List> test2 = new ArrayList<List>();
List<List> test3 = new ArrayList<List>();


test.add("pig");
test2.add(test);
test3.add(test2);

//System.out.println( ((List) ((List)(test3.get(0).get(0))).get(0)).set(0,"cow") );


__________________________________________________ ___

i've seem to asked a question on this in another thread. but here i'm asking for a different approach to solve the problem. given this construction, how do i change the value from "pig" to "cow"?? i'm sure there's some way to cast the List to accept and replace my string

[Norm]

//System.out.println( ((List) ((List)(test3.get(0).get(0))).get(0)).set(0,"cow") );
Break this down into single statements like the following:
Type1 var1 = var0.method();
Type2 var2 = var1.method();
Type3 var3 = var2.method();
etc
Then you can see what method of what class is being used.


Here's working code, but don't have good generics usage. Not sure if your approach is correct.

//how do i change the value from "pig" to "cow"

// Involves type checking and generics

import java.util.*;

public class TestIndexingLists {

	public static void main(String[] args) {
		ArrayList<String> test = new ArrayList<String>();
		List<List> test2 = new ArrayList<List>();
		List<List> test3 = new ArrayList<List>();
		
		test.add("pig");
		test2.add(test);
		test3.add(test2);
      //------------------------------------------------------------------------
      // get reference to test starting at test3
      List list_test2 = test3.get(0);
      System.out.println((test2 == list_test2) + "  list_test2:" 
                + list_test2.getClass());  // true list_test2:class java.util.ArrayList

      //-----------------------------------------------------------------------
//      ArrayList<String> list_testX = (ArrayList<String>)((ArrayList<List>)test2).get(0);
      ArrayList<String> list_testX = (ArrayList<String>)test2.get(0);
      //TestIndexingLists.java:24: warning: [unchecked] unchecked cast
      //found   : java.util.List                       <<< NB a List for test2 (a List<List>)
      //required: java.util.ArrayList<java.lang.String>
      //      ArrayList<String> list_testX = (ArrayList<String>)test2.get(0);
      //                                                                 ^

      ArrayList<String> list_test = (ArrayList<String>)list_test2.get(0);
      //TestIndexingLists.java:26: warning: [unchecked] unchecked cast
      //found   : java.lang.Object                      <<<< NB Object for list_test2 (a List<Object>)
      //required: java.util.ArrayList<java.lang.String>
      //      ArrayList<String> list_test = (ArrayList<String>)list_test2.get(0);
      //                                                                     ^
      //TestIndexingLists.java:21: inconvertible types
      //found   : java.util.List<java.util.List>
      //required: java.util.ArrayList<java.lang.String>
      //      ArrayList<String> list_test = ((ArrayList<String>)test2).get(0);
      //                                                        ^

// Changed source by removing ()before .get()
//TestIndexingLists.java:23: warning: [unchecked] unchecked cast
//found   : java.lang.Object
//required: java.util.ArrayList<java.lang.String>
//      ArrayList<String> list_test = (ArrayList<String>)list_test2.get(0);
//                                                                     ^

      System.out.println(test == list_test);     // true

      System.out.println(list_test);   // [pig]
      list_test.set(0, "cow");  // change pig to cow
      System.out.println(list_test);   // [cow]
	}
}