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Java : SequencedCollection with Examples

Published : December 21, 2023

SequencedCollection (Java SE 21 & JDK 21) with Examples.
You will find code examples on most SequencedCollection methods.


Summary

A collection that has a well-defined encounter order, that supports operations at both ends, and that is reversible. The elements of a sequenced collection have an encounter order, where conceptually the elements have a linear arrangement from the first element to the last element.

SequencedCollection (Java SE 21 & JDK 21)

Class diagram

final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("a");
sc.addLast("b");
sc.addLast("c");

System.out.println(sc); // [a, b, c]
System.out.println(sc.reversed()); // [c, b, a]

sc.addFirst("X");
sc.addFirst("Y");
sc.addFirst("Z");

System.out.println(sc); // [Z, Y, X, a, b, c]
System.out.println(sc.reversed()); // [c, b, a, X, Y, Z]

Methods

default void addFirst (E e)

Adds an element as the first element of this collection (optional operation).

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addFirst("aaa");
System.out.println(sc); // [aaa]

sc.addFirst("bbb");
System.out.println(sc); // [bbb, aaa]

sc.addFirst("ccc");
System.out.println(sc); // [ccc, bbb, aaa]

default void addLast (E e)

Adds an element as the last element of this collection (optional operation).

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("aaa");
System.out.println(sc); // [aaa]

sc.addLast("bbb");
System.out.println(sc); // [aaa, bbb]

sc.addLast("ccc");
System.out.println(sc); // [aaa, bbb, ccc]

default E getFirst ()

Gets the first element of this collection.

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("aaa");

System.out.println(sc); // [aaa]
System.out.println(sc.getFirst()); // aaa

sc.addLast("bbb");

System.out.println(sc); // [aaa, bbb]
System.out.println(sc.getFirst()); // aaa

sc.addLast("ccc");

System.out.println(sc); // [aaa, bbb, ccc]
System.out.println(sc.getFirst()); // aaa

final SequencedCollection<String> sc = new ArrayList<>();
System.out.println(sc); // []

try {
    final var ret = sc.getFirst();
} catch (NoSuchElementException e) {
    System.out.println("NoSuchElementException!");
}

// Result
// ↓
//NoSuchElementException!

default E getLast ()

Gets the last element of this collection.

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("aaa");

System.out.println(sc); // [aaa]
System.out.println(sc.getLast()); // aaa

sc.addLast("bbb");

System.out.println(sc); // [aaa, bbb]
System.out.println(sc.getLast()); // bbb

sc.addLast("ccc");

System.out.println(sc); // [aaa, bbb, ccc]
System.out.println(sc.getLast()); // ccc

final SequencedCollection<String> sc = new ArrayList<>();
System.out.println(sc); // []

try {
    final var ret = sc.getLast();
} catch (NoSuchElementException e) {
    System.out.println("NoSuchElementException!");
}

// Result
// ↓
//NoSuchElementException!

default E removeFirst ()

Removes and returns the first element of this collection (optional operation).

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("aaa");
sc.addLast("bbb");
sc.addLast("ccc");

System.out.println(sc); // [aaa, bbb, ccc]

System.out.println(sc.removeFirst()); // aaa
System.out.println(sc); // [bbb, ccc]

System.out.println(sc.removeFirst()); // bbb
System.out.println(sc); // [ccc]

System.out.println(sc.removeFirst()); // ccc
System.out.println(sc); // []

final SequencedCollection<String> sc = new ArrayList<>();
System.out.println(sc); // []

try {
    final var ret = sc.removeFirst();
} catch (NoSuchElementException e) {
    System.out.println("NoSuchElementException!");
}

// Result
// ↓
//NoSuchElementException!

default E removeLast ()

Removes and returns the last element of this collection (optional operation).

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("aaa");
sc.addLast("bbb");
sc.addLast("ccc");

System.out.println(sc); // [aaa, bbb, ccc]

System.out.println(sc.removeLast()); // ccc
System.out.println(sc); // [aaa, bbb]

System.out.println(sc.removeLast()); // bbb
System.out.println(sc); // [aaa]

System.out.println(sc.removeLast()); // aaa
System.out.println(sc); // []

final SequencedCollection<String> sc = new ArrayList<>();
System.out.println(sc); // []

try {
    final var ret = sc.removeLast();
} catch (NoSuchElementException e) {
    System.out.println("NoSuchElementException!");
}

// Result
// ↓
//NoSuchElementException!

SequencedCollection<E> reversed ()

Returns a reverse-ordered view of this collection.

SequencedCollection (Java SE 21 & JDK 21) 
final SequencedCollection<String> sc = new ArrayList<>();

sc.addLast("aaa");
sc.addLast("bbb");
sc.addLast("ccc");

System.out.println(sc); // [aaa, bbb, ccc]

final var reversedSc = sc.reversed();
System.out.println(reversedSc); // [ccc, bbb, aaa]

System.out.println(reversedSc.reversed()); // [aaa, bbb, ccc]

Methods declared in Collection

add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray

Please see the link below.

Methods declared in Iterable

forEach

Please see the link below.


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