Collection

[neha. bajaj]

Hello,
ArrayList class has size() and get() methods, so to invoke these methods on an ArrayList object is fine but how this is going on a List interface reference ?

String [] sa = {"one", "two", "three", "four"};
List sList = Arrays.asList(sa);                  // make a List
System.out.println("size  " + sList.size());
System.out.println("idx2  " + sList.get(2));

sList.set(3,"six");                             // change List
sa[l] = "five";                                 // change array
for(String s : sa)
  System.out.print(s + " ");
System.out.println("\nsl[1] " + sList.get(1));

This produces

size 4
idx2 three
one five three six
sl[1] five

[Aniruddh Joshi]

Both these methods are declared in the List interface. Check the javadoc

[Seetharaman Venkatasamy]

neha. bajaj wrote:Hello,
ArrayList class has size() and get() methods, so to do invoke these methods on an ArrayList object is fine but how this is going on an List interface reference ?

because, ArrayList implements List and List declare get,size methods.

I assume you are also wondering how List changes are reflected in to backed array?
from asList javadoc:

Returns a fixed-size list backed by the specified array. (Changes to
* the returned list "write through" to the array.)

[Seetharaman Venkatasamy]

and Welcome to JavaRanch

[neha. bajaj]

Seetharaman Venkatasamy wrote:and Welcome to JavaRanch

Thank you Seetharaman.

[neha. bajaj]

        int[] i1=new int[]{3,2,1,5,4,7,9};
		List l=Arrays.asList(i1);
		for(Object o:l)
			System.out.println(o);

output [I@1172e08

How to get output of this code in some meaningful way ?

[Seetharaman Venkatasamy]

for(Object o:l)  
	            System.out.println(Arrays.toString((int[])o));

[Rob Spoor]

Or by using proper generics you can get rid of the cast:

int[] i1=new int[]{3,2,1,5,4,7,9};
List<int[]> l=Arrays.asList(i1);
for (int[] array: l)
    System.out.println(Arrays.toString(array));

[Henry Wong]

Seetharaman Venkatasamy wrote:

for(Object o:l)  
	            System.out.println(Arrays.toString((int[])o));

Rob Spoor wrote:Or by using proper generics you can get rid of the cast:

int[] i1=new int[]{3,2,1,5,4,7,9};
List<int[]> l=Arrays.asList(i1);
for (int[] array: l)
    System.out.println(Arrays.toString(array));

I think that this may be a case of answering the question, but ignoring the problem -- as it seems that the OP is under the impression that the asList() method will convert an array of primitives into a list of wrapped objects.

Henry