List集合初始化

List集合初始化方式

1. 常规方式

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

2. Arrays 工具类

    // 生成的list不可变
    List<String> list = Arrays.asList("1", "2", "3");
    System.out.println("getList2: " + list);
    // 如果要可变需要用ArrayList包装一下
    List<String> numbers = new ArrayList<>(Arrays.asList("1", "2", "3"));
    numbers.add("4");
    System.out.println("numbers: " + numbers);

3. Collections 工具类

    // 生成的list不可变
    List<String> list = Collections.nCopies(3, "1");
    System.out.println("getList3: " + list);
    // 如果要可变需要用ArrayList包装一下
    List<String> dogs = new ArrayList<>(Collections.nCopies(3, "dog"));
    dogs.add("dog");
    System.out.println("dogs: " + dogs);

4. Lists 工具类

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

5. 匿名内部类

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

6. ImmutableList

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

7. Java8 Stream

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

8. Java9 List.of

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