Java ArrayDeque (Dengan Contoh)

Dalam tutorial ini, kita akan belajar mengenai kelas ArrayDeque dan kaedahnya dengan bantuan contoh. Juga, kita akan belajar menggunakan array deque untuk melaksanakan stack.

Di Java, kita dapat menggunakan ArrayDequekelas untuk menerapkan struktur data antrian dan deque menggunakan array.

Antara muka yang dilaksanakan oleh ArrayDeque

The ArrayDequekelas melaksanakan kedua-dua antara muka:

  • Antaramuka Antrian Java
  • Antaramuka Java Deque

Membuat ArrayDeque

Untuk membuat array deque, kita mesti mengimport java.util.ArrayDequepakej.

Inilah cara kita dapat membuat array deque di Java:

 ArrayDeque animal = new ArrayDeque();

Di sini, Type menunjukkan jenis array deque. Sebagai contoh,

 // Creating String type ArrayDeque ArrayDeque animals = new ArrayDeque(); // Creating Integer type ArrayDeque ArrayDeque age = new ArrayDeque();

Kaedah ArrayDeque

The ArrayDequekelas menyediakan pelaksanaan untuk semua kaedah di dalam Queuedan Dequeantara muka.

Masukkan Elemen ke Deque

1. Tambah elemen menggunakan add (), addFirst () dan addLast ()

  • add() - memasukkan elemen yang ditentukan pada akhir array deque
  • addFirst() - memasukkan elemen yang ditentukan pada awal array deque
  • addLast()- memasukkan yang ditentukan pada akhir array deque (setara dengan add())

Catatan: Sekiranya array larik penuh, semua kaedah ini add(), addFirst()dan addLast()lemparan IllegalStateException.

Sebagai contoh,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); // Using add() animals.add("Dog"); // Using addFirst() animals.addFirst("Cat"); // Using addLast() animals.addLast("Horse"); System.out.println("ArrayDeque: " + animals); ) )

Pengeluaran

 ArrayDeque: (Kucing, Anjing, Kuda)

2. Masukkan elemen menggunakan offer (), offerFirst () dan offerLast ()

  • offer() - memasukkan elemen yang ditentukan pada akhir array deque
  • offerFirst() - memasukkan elemen yang ditentukan pada awal array deque
  • offerLast() - memasukkan elemen yang ditentukan pada akhir array deque

Nota: offer() , offerFirst()dan offerLast()pulangan truejika unsur yang berjaya dimasukkan; jika array array penuh, kaedah ini akan kembali false.

Sebagai contoh,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); // Using offer() animals.offer("Dog"); // Using offerFirst() animals.offerFirst("Cat"); // Using offerLast() animals.offerLast("Horse"); System.out.println("ArrayDeque: " + animals); ) )

Pengeluaran

 ArrayDeque: (Kucing, Anjing, Kuda)

Catatan: Sekiranya susunan array penuh

  • yang add()kaedah akan membuang pengecualian
  • yang offer()pulangan kaedahfalse

Akses Elemen ArrayDeque

1. Akses elemen menggunakan getFirst () dan getLast ()

  • getFirst() - mengembalikan elemen pertama dari array array
  • getLast() - mengembalikan elemen terakhir dari array array

Catatan: Sekiranya array larik kosong, getFirst()dan getLast()melempar NoSuchElementException.

Sebagai contoh,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); animals.add("Dog"); animals.add("Cat"); animals.add("Horse"); System.out.println("ArrayDeque: " + animals); // Get the first element String firstElement = animals.getFirst(); System.out.println("First Element: " + firstElement); // Get the last element String lastElement = animals.getLast(); System.out.println("Last Element: " + lastElement); ) )

Pengeluaran

 ArrayDeque: (Anjing, Kucing, Kuda) Elemen Pertama: Elemen Terakhir Anjing: Kuda

2. Akses elemen menggunakan kaedah peek (), peekFirst () dan peekLast ()

  • peek() - mengembalikan elemen pertama dari array array
  • peekFirst()- mengembalikan elemen pertama array deque (bersamaan dengan peek())
  • peekLast() - mengembalikan elemen terakhir dari array array

Sebagai contoh,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); animals.add("Dog"); animals.add("Cat"); animals.add("Horse"); System.out.println("ArrayDeque: " + animals); // Using peek() String element = animals.peek(); System.out.println("Head Element: " + element); // Using peekFirst() String firstElement = animals.peekFirst(); System.out.println("First Element: " + firstElement); // Using peekLast String lastElement = animals.peekLast(); System.out.println("Last Element: " + lastElement); ) )

Pengeluaran

 ArrayDeque: (Anjing, Kucing, Kuda) Elemen Kepala: Elemen Pertama Anjing: Elemen Terakhir Anjing: Kuda

Nota: Jika deque array kosong, peek(), peekFirst()dan getLast()melemparkan NoSuchElementException.

Keluarkan Elemen ArrayDeque

1. Keluarkan elemen menggunakan kaedah remove (), removeFirst (), removeLast ()

  • remove() - mengembalikan dan mengeluarkan unsur dari elemen pertama dari array deque
  • remove(element) - mengembalikan dan mengeluarkan elemen yang ditentukan dari kepala deque array
  • removeFirst()- mengembalikan dan mengeluarkan elemen pertama dari array deque (setara dengan remove())
  • removeLast() - mengembalikan dan mengeluarkan elemen terakhir dari array deque

Note: If the array deque is empty, remove(), removeFirst() and removeLast() method throws an exception. Also, remove(element) throws an exception if the element is not found.

For example,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); animals.add("Dog"); animals.add("Cat"); animals.add("Cow"); animals.add("Horse"); System.out.println("ArrayDeque: " + animals); // Using remove() String element = animals.remove(); System.out.println("Removed Element: " + element); System.out.println("New ArrayDeque: " + animals); // Using removeFirst() String firstElement = animals.removeFirst(); System.out.println("Removed First Element: " + firstElement); // Using removeLast() String lastElement = animals.removeLast(); System.out.println("Removed Last Element: " + lastElement); ) )

Output

 ArrayDeque: (Dog, Cat, Cow, Horse) Removed Element: Dog New ArrayDeque: (Cat, Cow, Horse) Removed First Element: Cat Removed Last Element: Horse

2. Remove elements using the poll(), pollFirst() and pollLast() method

  • poll() - returns and removes the first element of the array deque
  • pollFirst() - returns and removes the first element of the array deque (equivalent to poll())
  • pollLast() - returns and removes the last element of the array deque

Note: If the array deque is empty, poll(), pollFirst() and pollLast() returns null if the element is not found.

For example,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); animals.add("Dog"); animals.add("Cat"); animals.add("Cow"); animals.add("Horse"); System.out.println("ArrayDeque: " + animals); // Using poll() String element = animals.poll(); System.out.println("Removed Element: " + element); System.out.println("New ArrayDeque: " + animals); // Using pollFirst() String firstElement = animals.pollFirst(); System.out.println("Removed First Element: " + firstElement); // Using pollLast() String lastElement = animals.pollLast(); System.out.println("Removed Last Element: " + lastElement); ) )

Output

 ArrayDeque: (Dog, Cat, Cow, Horse) Removed Element: Dog New ArrayDeque: (Cat, Cow, Horse) Removed First Element: Cat Removed Last Element: Horse

3. Remove Element: using the clear() method

To remove all the elements from the array deque, we use the clear() method. For example,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); animals.add("Dog"); animals.add("Cat"); animals.add("Horse"); System.out.println("ArrayDeque: " + animals); // Using clear() animals.clear(); System.out.println("New ArrayDeque: " + animals); ) )

Output

 ArrayDeque: (Dog, Cat, Horse) New ArrayDeque: ()

Iterating the ArrayDeque

  • iterator() - returns an iterator that can be used to iterate over the array deque
  • descendingIterator() - returns an iterator that can be used to iterate over the array deque in reverse order

In order to use these methods, we must import the java.util.Iterator package. For example,

 import java.util.ArrayDeque; import java.util.Iterator; class Main ( public static void main(String() args) ( ArrayDeque animals= new ArrayDeque(); animals.add("Dog"); animals.add("Cat"); animals.add("Horse"); System.out.print("ArrayDeque: "); // Using iterator() Iterator iterate = animals.iterator(); while(iterate.hasNext()) ( System.out.print(iterate.next()); System.out.print(", "); ) System.out.print("ArrayDeque in reverse order: "); // Using descendingIterator() Iterator desIterate = animals.descendingIterator(); while(desIterate.hasNext()) ( System.out.print(desIterate.next()); System.out.print(", "); ) ) )

Output

 ArrayDeque: (Dog, Cat, Horse) ArrayDeque in reverse order: (Horse, Cat, Dog)

Other Methods

Methods Descriptions
element() Returns an element from the head of the array deque.
contains(element) Searches the array deque for the specified element.
If the element is found, it returns true, if not it returns false.
size() Returns the length of the array deque.
toArray() Converts array deque to array and returns it.
clone() Creates a copy of the array deque and returns it.

ArrayDeque as a Stack

To implement a LIFO (Last-In-First-Out) stacks in Java, it is recommended to use a deque over the Stack class. The ArrayDeque class is likely to be faster than the Stack class.

ArrayDeque provides the following methods that can be used for implementing a stack.

  • push() - adds an element to the top of the stack
  • peek() - returns an element from the top of the stack
  • pop() - returns and removes an element from the top of the stack

For example,

 import java.util.ArrayDeque; class Main ( public static void main(String() args) ( ArrayDeque stack = new ArrayDeque(); // Add elements to stack stack.push("Dog"); stack.push("Cat"); stack.push("Horse"); System.out.println("Stack: " + stack); // Access element from top of stack String element = stack.peek(); System.out.println("Accessed Element: " + element); // Remove elements from top of stack String remElement = stack.pop(); System.out.println("Removed element: " + remElement); ) )

Output

 Stack: (Horse, Cat, Dog) Accessed Element: Horse Removed Element: Horse

ArrayDeque Vs. LinkedList Class

Both ArrayDeque and Java LinkedList implements the Deque interface. However, there exist some differences between them.

  • LinkedList supports null elements, whereas ArrayDeque doesn't.
  • Setiap nod dalam senarai terpaut merangkumi pautan ke nod lain. Itulah sebabnya LinkedListmemerlukan lebih banyak simpanan daripada ArrayDeque.
  • Sekiranya anda mengimplementasikan antrian atau struktur data deque, ArrayDequekemungkinan akan lebih cepat daripada a LinkedList.

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