How to Create a List in Java
There are many ways to initialize lists in Java. Here, we’ll get an idea of how to create a new ArrayList
.
Note that there are many different List
implementations, each of which have their own benefits.
List a = new ArrayList();
List b = new LinkedList();
List c = new Vector();
List d = new Stack();
List e = new CopyOnWriteArrayList();
1. Empty, mutable list
new ArrayList<>();
Lists.newArrayList(); // Guava
2. Empty, immutable list
Collections.emptyList();
Collections.EMPTY_LIST;
3. Non-empty, mutable list
new ArrayList<>(Arrays.asList(1,2)); // Java 8
new ArrayList<>(List.of(1,2)); // Java 9
Lists.newArrayList(1, 2); // Guava
4. Non-empty, fixed size list
Arrays.asList(1,2); // Java 8
List.of(1,2); // Java 9
Lists.asList(1, 2); // Guava
Lists.asList(1, new int[] { 2, 3 }); // Guava
Ints.asList(new int[] { 1, 2, 3 }); // Guava
5. Non-empty, immutable list
Collections.unmodifiableList(Arrays.asList(1,2));
ImmutableList.of(1,2); // Guava
ImmutableList.of(Lists.newArrayList(1,2)); // Guava
ImmutableList.builder() // Guava
.add(1)
.add(2)
.build();
Collections.singletonList(1); // Serializable