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An article explaining 8 ways to initialize a List collection in Java (with code)
An article explaining 8 ways to initialize a List collection in Java (with code)
In the previous article "A Brief Analysis of Server Code Deployment in Linux (Sharing)", we learned about server code deployment in Linux. The following article will give you an understanding of the 8 ways to initialize a List collection in Java. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
List is a commonly used collection in development. The following are several ways to initialize List.
Normal way
List<String> list = new ArrayList<>();
list.add("1");
list.add("2");
list.add("3");
System.out.println("getList1: " + list);Output
getList1: [1, 2, 3]
Arrays Tool Class
// 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);Output
getList2: [1, 2, 3] numbers: [1, 2, 3, 4]
Collections Tool Class
// 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);Output
getList3: [1, 1, 1] dogs: [dog, dog, dog, dog]
Lists Tool Class
List<String> list = Lists.newArrayList("1", "2", "3");
System.out.println("getList4: " + list);Output
getList4: [1, 2, 3]
Anonymous inner class
List<String> list = new ArrayList<String>() {{
add("1");
add("2");
add("3");
}};
System.out.println("getList5: " + list);Output
getList5: [1, 2, 3]
ImmutableList
List<String> list = ImmutableList.of("1", "2", "3");
System.out.println("getList6: " + list);Output
getList6: [1, 2, 3]
Java8 Stream
List<String> list = Stream.of("1", "2", "3").collect(Collectors.toList());
System.out.println("getList7: " + list);Output
getList7: [1, 2, 3]
Java9 List.of
List<String> list = List.of{"1", "2", "3"};
System.out.println("getList8: " + list);Output
getList8: [1, 2, 3]
Recommended learning: Java video tutorial
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