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Editor to share with you what are the ways to initialize the List collection in Java, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

List is a common collection in development. Here are several ways to initialize List.

Conventional mode

List list = new ArrayList (); list.add ("1"); list.add ("2"); list.add ("3"); System.out.println ("getList1:" + list)

Output

GetList1: [1, 2, 3]

Arrays utility class

/ the generated list immutable List list = Arrays.asList ("1", "2", "3"); System.out.println ("getList2:" + list); / / if you need to wrap List numbers = new ArrayList (Arrays.asList ("1", "2", "3")) in ArrayList if you want to change it; numbers.add ("4"); System.out.println ("numbers:" + numbers)

Output

GetList2: [1, 2, 3] numbers: [1, 2, 3, 4]

Collections utility class

/ the generated list immutable List list = Collections.nCopies (3, "1"); System.out.println ("getList3:" + list); / / if you need to wrap it in ArrayList, List dogs = new ArrayList (Collections.nCopies (3, "dog"); dogs.add ("dog"); System.out.println ("dogs:" + dogs)

Output

GetList3: [1, 1, 1] dogs: [dog, dog]

Lists utility class

List list = Lists.newArrayList ("1", "2", "3"); System.out.println ("getList4:" + list)

Output

GetList4: [1, 2, 3]

Anonymous inner class

List list = new ArrayList () {{add ("1"); add ("2"); add ("3");}}; System.out.println ("getList5:" + list)

Output

GetList5: [1, 2, 3]

ImmutableList

List list = ImmutableList.of ("1", "2", "3"); System.out.println ("getList6:" + list)

Output

GetList6: [1, 2, 3]

Java8 Stream

List list = Stream.of ("1", "2", "3"). System.out.println (Collectors.toList ()); System.out.println ("getList7:" + list)

Output

GetList7: [1, 2, 3]

Java9 List.of

List list = List.of {"1", "2", "3"}; System.out.println ("getList8:" + list)

Output

GetList8: [1, 2, 3] the above is all the contents of the article "what are the ways to initialize List collections in Java". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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