String array to arraylist

[Junilu Lacar]

B Verma wrote:

Campbell Ritchie wrote:Welcome to the Ranch

I wasn’t aware of that class; there are all sorts of useful things hiding away in the Apache project.

Thanks Campbell, yes indeed these Apache classes are having lot of useful utilities worth exploring.

Apache classes are useful - true that. However, I would think twice before using ConverterUtil.toList over some of the ways suggested before that use standard Java. ConverterUtil smells of NIH (Not Invented Here). I may be wrong and there may be perfectly legitimate reasons for its existence in the Apache project but I would question the need to suddenly create a dependency on Apache Axis just because you want to convert an array to a List. That's a bit of a stretch for an old guy like me who can't even reach his toes without bending his knees anymore.

[B Verma]

I do agree with you Junilu.

[caushik conjetty sekhar]

Janarthan S Sathiamurthy wrote:import java.util.Collections;

List myList = new ArrayList();
String[] myStringArray = new String[] {"Java", "is", "Cool"};

Collections.addAll(myList, myStringArray);

After this code, 'myList' should contain all the elements from the array.

Best regards,
Janarthan S

very good thread!

[Sumit Kayat]

Janarthan S Sathiamurthy wrote:import java.util.Collections;

List myList = new ArrayList();
String[] myStringArray = new String[] {"Java", "is", "Cool"};

Collections.addAll(myList, myStringArray);

After this code, 'myList' should contain all the elements from the array.

Best regards,
Janarthan S

Its Not Complied ... 2 Notes Shown
1 java Uses unchecked and Unsafe Opeations
2Recompile with Xlint
help out

[Harinder Bedi]

Jesper de Jong wrote:There are some important things to note with the solutions given above:

Garrett's solution, with Arrays.asList() is efficient because it doesn't need to copy the content of the array. This method returns a List that is a "view" onto the array - a wrapper that makes the array look like a list. When you change an element in the list, the element in the original array is also changed. Note that the list is fixed size - if you try to add elements to the list, you'll get an exception.

Ernest's solution: new ArrayList(Arrays.asList(myArray)); copies the content of the array to a new ArrayList. The copy is ofcourse independent of the array, and you can add, remove etc. elements as you like.

Janarthan's solution, with Collections.addAll(myList, myStringArray); is essentially the same as Ernest's solution.

If you only need read access to the array as if it is a List and you don't want to add or remove elements from the list, then use Garrett's solution. Otherwise use Ernest's or Janarthan's solution.

Thanks for the info.

[diksha singh neel]

Declare an arraylist, take the size of the array, loop that many times and enter elements one by one into the arraylist.

[Scott Shipp]

As the old saying goes there's more than one way to skin a cat..

[Prasad Saya]

Jesper de Jong wrote:There are some important things to note with the solutions given above:

Garrett's solution, with Arrays.asList() is efficient because it doesn't need to copy the content of the array. This method returns a List that is a "view" onto the array - a wrapper that makes the array look like a list. When you change an element in the list, the element in the original array is also changed. Note that the list is fixed size - if you try to add elements to the list, you'll get an exception.

Ernest's solution: new ArrayList(Arrays.asList(myArray)); copies the content of the array to a new ArrayList. The copy is ofcourse independent of the array, and you can add, remove etc. elements as you like.

Janarthan's solution, with Collections.addAll(myList, myStringArray); is essentially the same as Ernest's solution.

If you only need read access to the array as if it is a List and you don't want to add or remove elements from the list, then use Garrett's solution. Otherwise use Ernest's or Janarthan's solution.

As of Java 8:

String [] strings = {"one", "two", "three"};

List<String> list_1 = Arrays.asList("one", "two", "three");
List<String> list_1a = Arrays.asList(strings);
list_1.add("nine"); // NOTE: this throws java.lang.UnsupportedOperationException

Note, this is already explained in the post by Jesper de Jong. This is because (from the API javadocs) the method Arrays.asList() returns a fixed-size list (list_1 or list_1a) backed by the specified array. Of course, this can be overcome by using this construct:
List<String> list_1c = new ArrayList<>(Arrays.asList(strings));


Using Streams:

List<String> list_2a = Arrays.stream(strings).collect(asList());
List<String> list_2b = Stream.of(strings).collect(asList());
List<String> list_2c = Stream.of(strings).collect(toCollection(LinkedList::new));
list_2a.add("nine"); // No exceptions here

Note, the statement above at line 3 (creating list_2c) allows to specify the type of List implementation, in this case a LinkedList.

NOTE: For the above statements building the List, instead of an array, varargs can be specified. The behaviour remains the same.