Java 中初始化 List 集合的 8 種方式!

List 是在開發中比較常用的集合，今天總結一下 Java 中初始化 List 的幾種方式。

1、常規方式

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

輸出

getList1: [1, 2, 3] 

2、Arrays 工具類

// 生成的list不可變 List<String> list = Arrays.asList("1", "2", "3"); System.out.println("getList2: " + list); // 如果要可變需要用ArrayList包裝一下 List<String> numbers = new ArrayList<>(Arrays.asList("1", "2", "3")); numbers.add("4"); System.out.println("numbers: " + numbers); 

輸出

getList2: [1, 2, 3] numbers: [1, 2, 3, 4] 

3、Collections 工具類

// 生成的list不可變 List<String> list = Collections.nCopies(3, "1"); System.out.println("getList3: " + list); // 如果要可變需要用ArrayList包裝一下 List<String> dogs = new ArrayList<>(Collections.nCopies(3, "dog")); dogs.add("dog"); System.out.println("dogs: " + dogs); 

輸出

getList3: [1, 1, 1] dogs: [dog, dog, dog, dog] 

4、Lists 工具類

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

輸出

getList4: [1, 2, 3] 

5、匿名內部類

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

輸出

getList5: [1, 2, 3] 

6、ImmutableList

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

輸出

getList6: [1, 2, 3] 

7、Java8 Stream

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

輸出

getList7: [1, 2, 3] 

8、Java9 List.of

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

輸出

getList8: [1, 2, 3]