Collection Types

Commonly used collection types in Rust and their mapping to Java:

Notes:

1. Java provides the Arrays utility class for manipulating arrays.

2. Unlike Rust, Java does not have the Tuple type.

3. In both Rust and Java the LinkedList collection is implemented using a doubly-linked list.

Arrays

Fixed arrays are supported the same way in Rust and Java.

Java:

int[] someArray = new int[] { 1, 2 };

Rust:

let some_array: [i32; 2] = [1,2];

Notice the type of some_array: [T; N] - it indicates both the type of elements of the array and the size of the array (which is fixed at compile time).

Accessing array elements is similar in both languages:

Java:

int firstElement = someArray[0];
int secondElement = someArray[1];

System.out.println(firstElement);  // prints: 1
System.out.println(secondElement); // prints: 2

Rust:

let first_element = some_array[0];
let second_element = some_array[1];

println!("{}", first_element);  // prints: 1
println!("{}", second_element); // prints: 2

ArrayList

In Rust, the equivalent of Java's ArrayList<E> is Vec<T>. Arrays can be converted to Vecs and vice versa.

Java:

List<String> someList = new ArrayList<>(Arrays.asList("a", "b"));

someList.add("c");

Rust:

let mut some_list = vec![
    "a".to_owned(),
    "b".to_owned()
];

some_list.push("c".to_owned());

HashMap

In both Rust and Java, a HashMap is represented as HashMap<K, V>.

Java:

Map<String, String> someMap = new HashMap<>(Map.of("Foo", "Bar", "Baz", "Qux"));

someMap.put("hi", "there");

Rust:

let mut some_map = HashMap::from([
    ("Foo".to_owned(), "Bar".to_owned()),
    ("Baz".to_owned(), "Qux".to_owned())
]);

some_map.insert("hi".to_owned(), "there".to_owned());

HashSet

In Rust, the equivalent of Java's HashSet<E> is HashSet<T>.

Java:

Set<String> someSet = new HashSet<>(Set.of("a", "b"));

someSet.add("c");

Rust:

let mut some_set = HashSet::from(["a".to_owned(), "b".to_owned()]);

some_set.insert("c".to_owned());

See also:

• Rust's standard library - Collections