What are the ways to initialize List collections in Java
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!
