Java ArrayDeque (s primjerima)

U ovom uputstvu uz primjere ćemo naučiti o klasi ArrayDeque i njezinim metodama. Također, naučit ćemo koristiti deque niza za implementaciju stoga.

U Javi ArrayDequeklasu možemo koristiti za implementaciju struktura podataka u redu i uklanjanju pomoću nizova.

Sučelja koja implementira ArrayDeque

ArrayDequeKlasa implementira ova dva sučelja:

  • Sučelje Java Queue
  • Java Deque sučelje

Stvaranje ArrayDeque

Da bismo stvorili deque niza, moramo uvesti java.util.ArrayDequepaket.

Evo kako možemo stvoriti deque niza u Javi:

 ArrayDeque animal = new ArrayDeque();

Ovdje Type označava tip deque polja. Na primjer,

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

Metode ArrayDeque

ArrayDequeKlasa pruža implementacije za sve metode prisutan u Queuei Dequesučelje.

Umetnite elemente u Deque

1. Dodajte elemente pomoću add (), addFirst () i addLast ()

  • add() - ubacuje navedeni element na kraj deque polja
  • addFirst() - ubacuje navedeni element na početak niza polja
  • addLast()- ubacuje specificirani na kraj deque polja (ekvivalentno add())

Napomena: Ako je polje deque puna, sve ove metode add(), addFirst()i addLast()baca IllegalStateException.

Na primjer,

 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); ) )

Izlaz

 ArrayDeque: (Mačka, Pas, Konj)

2. Umetnite elemente pomoću offer (), offerFirst () i offerLast ()

  • offer() - ubacuje navedeni element na kraj deque polja
  • offerFirst() - ubacuje navedeni element na početak niza polja
  • offerLast() - ubacuje navedeni element na kraj deque polja

Napomena: offer() , offerFirst()a offerLast()vraća trueako je element uspješno je umetnut; ako je niz deque pun, ove se metode vraćaju false.

Na primjer,

 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); ) )

Izlaz

 ArrayDeque: (Mačka, Pas, Konj)

Napomena: Ako je deque polja pun

  • add()način će se baciti iznimku
  • je offer()metoda vraćafalse

Pristupite elementima ArrayDeque

1. Pristupite elementima pomoću getFirst () i getLast ()

  • getFirst() - vraća prvi element deque niza
  • getLast() - vraća zadnji element deque niza

Napomena: Ako je niz deque prazan getFirst()i getLast()baca NoSuchElementException.

Na primjer,

 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); ) )

Izlaz

 ArrayDeque: (Pas, Mačka, Konj) Prvi element: Pas Zadnji element: Konj

2. Pristupite elementima pomoću metoda peek (), peekFirst () i peekLast ()

  • peek() - vraća prvi element deque niza
  • peekFirst()- vraća prvi element niza deque (ekvivalentno peek())
  • peekLast() - vraća zadnji element deque niza

Na primjer,

 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); ) )

Izlaz

 ArrayDeque: (pas, mačka, konj) Element glave: pas prvi element: pas posljednji element: konj

Napomena: Ako je polje deque je prazna, peek(), peekFirst()i getLast()baca NoSuchElementException.

Uklonite ArrayDeque elemente

1. Uklonite elemente metodom remove (), removeFirst (), removeLast ()

  • remove() - vraća i uklanja element iz prvog elementa deque niza
  • remove(element) - vraća i uklanja navedeni element iz glave niza deque
  • removeFirst()- vraća i uklanja prvi element iz niza deque (ekvivalentno remove())
  • removeLast() - vraća i uklanja posljednji element iz niza polja

Napomena: Ako je polje deque je prazna, remove(), removeFirst()i removeLast()metoda baca iznimku. Također, remove(element)baca iznimku ako element nije pronađen.

Na primjer,

 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); ) )

Izlaz

 ArrayDeque: (Pas, Mačka, Krava, Konj) Uklonjeni element: Pas Novi ArrayDeque: (Mačka, Krava, Konj) Uklonjen Prvi element: Mačka Uklonjen Posljednji element: Konj

2. Uklonite elemente metodom poll (), pollFirst () i pollLast ()

  • poll() - vraća i uklanja prvi element deque niza
  • pollFirst()- vraća i uklanja prvi element deque niza (ekvivalentno poll())
  • pollLast() - vraća i uklanja posljednji element deque niza

Napomena: Ako je polje deque je prazna, poll(), pollFirst()i pollLast()vraća nullako element nije pronađen.

Na primjer,

 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); ) )

Izlaz

 ArrayDeque: (Pas, Mačka, Krava, Konj) Uklonjeni element: Pas Novi ArrayDeque: (Mačka, Krava, Konj) Uklonjen Prvi element: Mačka Uklonjen Posljednji element: Konj

3. Uklonite element: metodom clear ()

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.
  • Svaki čvor na povezanom popisu uključuje veze do drugih čvorova. Zato je LinkedListpotrebno više prostora za pohranu ArrayDeque.
  • Ako implementirate red čekanja ili strukturu podataka deque, an ArrayDequeće vjerojatno biti brži od a LinkedList.

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