ArrayDeque in Java[通俗易懂]

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发布于 2022-11-08 10:40:24

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发布于 2022-11-08 10:40:24

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ArrayDeque in Java

ArrayDeque in Java provides a way to apply resizable-array in addition to the implementation of the Deque interface. It is also known as Array Double Ended Queue or Array Deck. This is a special kind of array that grows and allows users to add or remove an element from both the sides of the queue. Few important features of ArrayDeque are as follows:

Array deques have no capacity restrictions and they grow as necessary to support usage.
They are not thread-safe which means that in the absence of external synchronization, ArrayDeque does not support concurrent access by multiple threads.
Null elements are prohibited in the ArrayDeque.
ArrayDeque class is likely to be faster than Stack when used as a stack.
ArrayDeque class is likely to be faster than LinkedList when used as a queue.

Declaration:

public class ArrayDeque Element
   extends AbstractCollection
   implements DequeElement, Cloneable, Serializable

Here, Element refers to the element which can refer to any class, such as Integer or Stringclass.

Constructors in ArrayDeque:

ArrayDeque(): Used to create an empty ArrayDeque and by default holds an initial capacity to hold 16 elements.
ArrayDeque(Collection c): Used to create an ArrayDeque containing all the elements same as that of the specified collection.
ArrayDeque(int numofElements): Used to create an empty ArrayDeque wand holds the capacity to contain a specified number of elements.

Example:

// Java program to demonstrate few functions of 
// ArrayDeque in Java 

import java.util.*; 
public class ArrayDequeDemo 
{ 
	public static void main(String[] args) 
	{ 
		// Intializing an deque 
		Deque<Integer> de_que = new ArrayDeque<Integer>(10); 

		// add() method to insert 
		de_que.add(10); 
		de_que.add(20); 
		de_que.add(30); 
		de_que.add(40); 
		de_que.add(50); 
		for (Integer element : de_que) 
		{ 
			System.out.println("Element : " + element); 
		} 

		System.out.println("Using clear() "); 

		// clear() method 
		de_que.clear(); 

		// addFirst() method to insert at start 
		de_que.addFirst(564); 
		de_que.addFirst(291); 

		// addLast() method to insert at end 
		de_que.addLast(24); 
		de_que.addLast(14); 

		System.out.println("Above elements are removed now"); 

		// Iterator() : 
		System.out.println("Elements of deque using Iterator :"); 
		for(Iterator itr = de_que.iterator(); itr.hasNext();) 
		{ 
			System.out.println(itr.next()); 
		} 

		// descendingIterator() : to reverse the deque order 
		System.out.println("Elements of deque in reverse order :"); 
		for(Iterator dItr = de_que.descendingIterator(); 
											dItr.hasNext();) 
		{ 
			System.out.println(dItr.next()); 
		} 

		// element() method : to get Head element 
		System.out.println("\nHead Element using element(): " + 
											de_que.element()); 

		// getFirst() method : to get Head element 
		System.out.println("Head Element using getFirst(): " + 
											de_que.getFirst()); 

		// getLast() method : to get last element 
		System.out.println("Last Element using getLast(): " + 
												de_que.getLast()); 

		// toArray() method : 
		Object[] arr = de_que.toArray(); 
		System.out.println("\nArray Size : " + arr.length); 

		System.out.print("Array elements : "); 
		for(int i=0; i<arr.length ; i++) 
			System.out.print(" " + arr[i]); 
			
		// peek() method : to get head 
		System.out.println("\nHead element : " + de_que.peek()); 
		
		// poll() method : to get head 
		System.out.println("Head element poll : " + de_que.poll()); 
		
		// push() method : 
		de_que.push(265); 
		de_que.push(984); 
		de_que.push(2365); 
		
		// remove() method : to get head 
		System.out.println("Head element remove : " + de_que.remove()); 
		
		System.out.println("The final array is: "+de_que); 
	} 
}

Output:

Element : 10
Element : 20
Element : 30
Element : 40
Element : 50
Using clear() 
Above elements are removed now
Elements of deque using Iterator :
291
564
24
14
Elements of deque in reverse order :
14
24
564
291

Head Element using element(): 291
Head Element using getFirst(): 291
Last Element using getLast(): 14

Array Size : 4
Array elements :  291 564 24 14
Head element : 291
Head element poll : 291
Head element remove : 2365
The final array is: [984, 265, 564, 24, 14]

Methods in ArrayDeque:

add(Element e) : The method inserts particular element at the end of the deque.
addFirst(Element e) : The method inserts particular element at the start of the deque.
addLast(Element e) : The method inserts particular element at the end of the deque. It is similiar to add() method
clear() : The method removes all deque elements.
size() : The method returns the no. of elements in deque.
clone() : The method copies the deque.
contains(Obj) : The method checks whether a deque contains the element or not
Iterator() : The method returns an iterator over the deque.
descendingIterator() : The method returns a reverse order iterator over the deque
element() : The method returns element at the head of the deque
getFirst(): The method returns first element of the deque
getLast(): The method returns last element of the deque
isEmpty(): The method checks whether the deque is empty or not.
toArray(): The method returns array having the elements of deque.
offer(Element e) : The method inserts element at the end of deque.
offerFirst(Element e) : The method inserts element at the front of deque.
offerLast(Element e) : The method inserts element at the end of deque.
peek() : The method returns head element without removing it.
peekFirst() : The method returns first element without removing it.
peekLast() : The method returns last element without removing it.
poll() : The method returns head element and also removes it
pollFirst() : The method returns first element and also removes it
pollLast() : The method returns last element and also removes it
pop() : The method pops out an element for stack repesented by deque
push(Element e) : The method pushes an element onto stack repesented by deque
remove() : The method returns head element and also removes it
removeFirst() : The method returns first element and also removes it
removeLast() : The method returns last element and also removes it
removeFirstOccurrence(Obj) : The method removes the element where it first occur in the deque.
removeLastOccurrence(Obj) : The method removes the element where it last occur in the deque.

ArrayDeque addFirst() Method in Java

The java.util.ArrayDeque.addFirst(Object element) method in Java is used to insert a specific element at the front of this deque.

Syntax:

Array_Deque.addFirst(Object element)

Parameters: The parameter element is of the type ArrayDeque and refers to the element to be added.

Return Value: The function does not return any value.

Exceptions: The method throws NullPointerException if the passed parameter is NULL.

Below programs illustrate the Java.util.ArrayDeque.addFirst() method: Program 1:

// Java code to illustrate addFirst() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<Integer> de_que = new ArrayDeque<Integer>(); 

		// Use add() method to add elements into the Deque 
		de_que.add(10); 
		de_que.add(15); 
		de_que.add(30); 
		de_que.add(20); 
		de_que.add(5); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Adding elements at front 
		de_que.addFirst(40); 
		de_que.addFirst(50); 
		de_que.addFirst(60); 
		de_que.addFirst(70); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque_front_addition: " + de_que); 

		// Adding elements using add() 
		de_que.add(1); 
		de_que.add(2); 
		de_que.add(3); 

		// Displaying the final ArrayDeque 
		System.out.println("Final ArrayDeque: " + de_que); 
	} 
}

Output:

ArrayDeque: [10, 15, 30, 20, 5]
ArrayDeque_front_addition: [70, 60, 50, 40, 10, 15, 30, 20, 5]
Final ArrayDeque: [70, 60, 50, 40, 10, 15, 30, 20, 5, 1, 2, 3]

ArrayDeque add() Method in Java

The Java.util.ArrayDeque.add(Object element) method in Java is used to add a specific element at the end of the Deque. The function is similar to the addLast() method of ArrayDeque in Java.

Syntax:

Array_Deque.add(Object element)

Parameters: The parameter element is of the type ArrayDeque and refers to the element to be added to the Deque.

Return Value: The function returns True if the element is successfully added into the deque else it returns false.

Exceptions: The method throws NullPointerException if the passed parameter is NULL.

Below programs illustrate the Java.util.ArrayDeque.add() method: Program 1: Adding String elements into the Deque.

// Java code to illustrate add() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]

Program 2: Adding Integer elements into the Deque.

// Java code to illustrate add() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<Integer> de_que = new ArrayDeque<Integer>(); 

		// Use add() method to add elements into the Deque 
		de_que.add(10); 
		de_que.add(15); 
		de_que.add(30); 
		de_que.add(20); 
		de_que.add(5); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 
	} 
}

Output:

ArrayDeque: [10, 15, 30, 20, 5]

ArrayDeque addLast() Method in Java

The java.util.ArrayDeque.addLast(Object element) method in Java is used to insert a specific element at the end of this deque. It is similar to the add() method in Java.

Syntax:

Array_Deque.addLast(Object element)

Parameters: The parameter element is of the type ArrayDeque and refers to the element to be added.

Return Value: The function does not return any value.

Exceptions: The method throws NullPointerException if the passed parameter is NULL.

Below programs illustrate the Java.util.ArrayDeque.addLast() method: Program 1: Adding Integers to the Deque.

// Java code to illustrate addLast() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<Integer> de_que = new ArrayDeque<Integer>(); 

		// Use add() method to add elements into the Deque 
		de_que.add(10); 
		de_que.add(15); 
		de_que.add(30); 
		de_que.add(20); 
		de_que.add(5); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Adding elements at the end 
		de_que.addLast(40); 
		de_que.addLast(50); 
		de_que.addLast(60); 
		de_que.addLast(70); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque_end_addition: " + de_que); 
	} 
}

Output:

ArrayDeque: [10, 15, 30, 20, 5]
ArrayDeque_end_addition: [10, 15, 30, 20, 5, 40, 50, 60, 70]

ArrayDeque getFirst() Method in Java

The java.util.ArrayDeque.getFirst() method in Java is used to retrieve or fetch the first element of the ArrayDeque. In the process, the method does not delete the element from the deque instead it just returns the first element of the deque.

Syntax:

Array_Deque.getFirst()

Parameters: The method does not take any parameter.

Return Value: The method returns the first element present in the Deque.

Below programs illustrate the Java.util.ArrayDeque.getFirst() method:

Program 1:

// Java code to illustrate getFirst() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		ArrayDeque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Displaying the first element 
		System.out.println("The first element is: " + 
									de_que.getFirst()); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The first element is: Welcome

ArrayDeque isEmpty() Method in Java

The Java.util.ArrayDeque.isEmpty() method in Java is used to check and verify if an ArrayDeque is empty or not. It returns True if the Deque is empty else it returns False.

Syntax:

Array_Deque.isEmpty()

Parameters: The method does not take any parameter.

Return Value: The function returns True if the deque is empty else it returns False.

Below programs illustrate the Java.util.ArrayDeque.isEmpty() method:

Program 1:

// Java code to illustrate isEmpty() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Verifying if the Deque is empty or not 
		System.out.println("The Deque is empty? " + 
									de_que.isEmpty()); 

		// Clearing the deque 
		de_que.clear(); 

		// Verifying if the Deque is empty or not 
		System.out.println("The Deque is empty? " + 
									de_que.isEmpty()); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The Deque is empty? false
The Deque is empty? true

ArrayDeque clear() Method in Java

The Java.util.ArrayDeque.clear() method in Java is used to remove all of the elements from the Deque. Using the clear() method only clears all the element from the deque and does not delete the deque. In other words, it can be said that the clear() method is used to only empty an existing ArrayDeque.

Syntax:

Array_Deque.clear()

Parameters: The method does not take any parameter.

Return Value: The function does not return any value.

Below programs illustrate the Java.util.ArrayDeque.clear() method: Program 1:

// Java code to illustrate clear() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Clearing the Deque 
		de_que.clear(); 

		// Displaying the Deque 
		System.out.println("ArrayDeque: " + de_que); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
ArrayDeque: []

ArrayDeque size() Method in Java

The Java.util.ArrayDeque.size() method in Java is used to get the size of the Deque or the number of elements present in the Deque.

Syntax:

Array_Deque.size()

Parameters: The method does not take any parameter.

Return Value: The method returns the size or the number of elements present in the Deque.

Below programs illustrate the Java.util.ArrayDeque.size() method: Program 1: Adding String elements into the Deque.

// Java code to illustrate size() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Displaying the size of Deque 
		System.out.println("The size is: " + de_que.size()); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The size is: 5

ArrayDeque contains() Method in Java

The Java.util.ArrayDeque.contains() method in Java is used to check or verify whether a specific element is present in the Deque or not.

Syntax:

Array_Deque.contains(Object element)

Parameters: The parameter element is of the type of ArrayDeque. This is the element that needs to be tested if it is present in the deque or not.

Return Value: The method returns True if the element is present in the deque otherwise it returns False.

Below programs illustrate the Java.util.ArrayDeque.contains() method: Program 1:

// Java code to illustrate contains() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Queue 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Check for "Geeks" in the deque 
		System.out.println("Does the deque contains 'Geeks'? "
						+ de_que.contains("Geeks")); 

		// Check for "4" in the deque 
		System.out.println("Does the deque contains '4'? "
						+ de_que.contains("4")); 

		// Check if the deque contains "No" 
		System.out.println("Does the deque contains 'No'? "
						+ de_que.contains("No")); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
Does the deque contains 'Geeks'? true
Does the deque contains '4'? true
Does the deque contains 'No'? false

ArrayDeque iterator() Method in Java

The Java.util.ArrayDeque.iterator() method is used to return an iterator of the elements of the ArrayDeque.

Syntax:

Iterator iterate_value = Array_Deque.iterator();

Parameters: The method does not take any parameter.

Return Value: The method iterates over the elements of the deque and returns the values(iterator).

Below programs illustrate the Java.util.ArrayDeque.iterator() method: Program 1:

// Java code to illustrate iterator() 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		Deque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Queue 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Creating an iterator 
		Iterator value = de_que.iterator(); 

		// Displaying the values after iterating through the Deque 
		System.out.println("The iterator values are: "); 
		while (value.hasNext()) { 
			System.out.println(value.next()); 
		} 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The iterator values are: 
Welcome
To
Geeks
4
Geeks

ArrayDeque getLast() Method in Java

The java.util.ArrayDeque.getLast() method in Java is used to retrieve or fetch the last element of the ArrayDeque. In the process, the method does not delete the element from the deque instead it just returns the last element of the deque.

Syntax:

Array_Deque.getLast()

Parameters: The method does not take any parameter.

Return Value: The method returns the last element present in the Deque.

Below programs illustrate the Java.util.ArrayDeque.getLast() method:

Program 1:

// Java code to illustrate getLast() method of ArrayDeque 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		ArrayDeque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Displaying the Last element 
		System.out.println("The last element is: " + de_que.getLast()); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The last element is: Geeks

ArrayDeque element() Method in Java

The java.util.ArrayDeque.element() method in Java is used to retrieve or fetch the head of the ArrayDeque. In the process, the method does not delete the element from the deque instead it just returns the element.

Syntax:

Array_Deque.element()

Parameters: The method does not take any parameter.

Return Value: The method returns the element present at the head of the Deque.

Below programs illustrate the Java.util.ArrayDeque.element() method: Program 1:

// Java code to illustrate ArrayDeque element() method 
import java.util.*; 

public class ArrayDequeDemo { 
	public static void main(String args[]) 
	{ 
		// Creating an empty ArrayDeque 
		ArrayDeque<String> de_que = new ArrayDeque<String>(); 

		// Use add() method to add elements into the Deque 
		de_que.add("Welcome"); 
		de_que.add("To"); 
		de_que.add("Geeks"); 
		de_que.add("4"); 
		de_que.add("Geeks"); 

		// Displaying the ArrayDeque 
		System.out.println("ArrayDeque: " + de_que); 

		// Displaying the head 
		System.out.println("The head element is: " + de_que.element()); 
	} 
}

Output:

ArrayDeque: [Welcome, To, Geeks, 4, Geeks]
The head element is: Welcome

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原始发表：2022年9月20日，如有侵权请联系 cloudcommunity@tencent.com 删除

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ArrayDeque in Java[通俗易懂]

ArrayDeque in Java[通俗易懂]

ArrayDeque in Java

ArrayDeque addFirst() Method in Java

ArrayDeque add() Method in Java

ArrayDeque addLast() Method in Java

ArrayDeque getFirst() Method in Java

ArrayDeque isEmpty() Method in Java

ArrayDeque clear() Method in Java

ArrayDeque size() Method in Java

ArrayDeque contains() Method in Java

ArrayDeque iterator() Method in Java

ArrayDeque getLast() Method in Java

ArrayDeque element() Method in Java

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