How can I initialise a static Map?

To initialize a static Map in Java, you can use the Map interface's of method, which was added in Java 9. The of method creates an immutable Map with a fixed set of key-value pairs.

For example, to create a static Map that maps the strings "apple", "banana", and "cherry" to their respective lengths, you can use the following code:

---

static final Map<String, Integer> map = Map.of(
  "apple", 5,
  "banana", 6,
  "cherry", 6
);

This creates an immutable Map with three key-value pairs.

You can also use the Map.ofEntries method to create a Map from a collection of Map.Entry objects. For example:

---

static final Map<String, Integer> map = Map.ofEntries(
  Map.entry("apple", 5),
  Map.entry("banana", 6),
  Map.entry("cherry", 6
);

This creates an immutable Map with the same key-value pairs as the previous example.

Note that the Map objects created by the of and ofEntries methods are immutable, which means that you cannot modify the map after it is created. If you need a mutable map, you can use the HashMap class or one of the other mutable implementations. Because these maps are static and immutable, they are inherently thread-safe for read-only access.