Java ArrayDeque (z primeri)

V tej vadnici bomo s pomočjo primerov spoznali razred ArrayDeque in njegove metode. Prav tako se bomo naučili uporabljati deque matrike za izvedbo sklada.

V Javi lahko ArrayDequerazred uporabimo za izvedbo čakalnih vrst in deque podatkovnih struktur z uporabo nizov.

Vmesniki, ki jih izvaja ArrayDeque

ArrayDequeRazredu izvaja ta dva vmesnika:

  • Vmesnik Java Queue
  • Java Deque vmesnik

Ustvarjanje ArrayDeque

Če želimo ustvariti matriko, moramo java.util.ArrayDequepaket uvoziti .

Tukaj je opisano, kako lahko v Javi ustvarimo deque array:

 ArrayDeque animal = new ArrayDeque();

Tu Type označuje vrsto deque matrike. Na primer

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

Metode ArrayDeque

ArrayDequeRazred določa izvedbe za vse metode trenutno v Queuein Dequevmesnik.

Vstavite elemente v Deque

1. Dodajte elemente z uporabo add (), addFirst () in addLast ()

  • add() - vstavi navedeni element na konec matrike
  • addFirst() - vstavi določen element na začetek niza matrike
  • addLast()- vstavi določeno na koncu niza deque (enakovredno add())

Opomba: Če je matrika deque poln, vse te metode add(), addFirst()in addLast()meče IllegalStateException.

Na primer

 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); ) )

Izhod

 ArrayDeque: (mačka, pes, konj)

2. Vstavite elemente z uporabo offer (), offerFirst () in offerLast ()

  • offer() - vstavi navedeni element na konec matrike
  • offerFirst() - vstavi določen element na začetek niza matrike
  • offerLast() - vstavi navedeni element na konec matrike

Opomba: offer() , offerFirst()in offerLast()vrne true, če je uspešno vstavljen element; če je matrika polja polna, se te metode vrnejo false.

Na primer

 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); ) )

Izhod

 ArrayDeque: (mačka, pes, konj)

Opomba: Če je matrika polja polna

  • add()metoda bo vrgel izjemo
  • je offer()metoda vrnefalse

Dostopite do elementov ArrayDeque

1. Do elementov dostopajte z uporabo getFirst () in getLast ()

  • getFirst() - vrne prvi element deque matrike
  • getLast() - vrne zadnji element deque matrike

Opomba: Če je polje deque prazno getFirst()in getLast()vrže NoSuchElementException.

Na primer

 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); ) )

Izhod

 ArrayDeque: (pes, mačka, konj) prvi element: pes zadnji element: konj

2. Do elementov dostopajte z uporabo metod peek (), peekFirst () in peekLast ()

  • peek() - vrne prvi element deque matrike
  • peekFirst()- vrne prvi element niza deque (enakovredno peek())
  • peekLast() - vrne zadnji element deque matrike

Na primer

 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); ) )

Izhod

 ArrayDeque: (pes, mačka, konj) Element glave: pes prvi element: pes zadnji element: konj

Opomba: Če je matrika deque je prazna peek(), peekFirst()in getLast()meče NoSuchElementException.

Odstranite elemente ArrayDeque

1. Odstranite elemente z metodo remove (), removeFirst (), removeLast ()

  • remove() - vrne in odstrani element iz prvega elementa deque matrike
  • remove(element) - vrne in odstrani navedeni element iz glave niza matrike
  • removeFirst()- vrne in odstrani prvi element iz niza deque (enakovredno remove())
  • removeLast() - vrne in odstrani zadnji element iz niza matrike

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.
  • Vsako vozlišče na povezanem seznamu vključuje povezave do drugih vozlišč. Zato LinkedListzahteva več prostora kot ArrayDeque.
  • Če izvajate čakalno vrsto ali podatkovno strukturo deque, bo an ArrayDequeverjetno hitrejši od a LinkedList.

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