Array with linked list java

Implementing a Linked List using array in java?

I have read it in robbert laffore that we can implement Linked list using arrays as well. But the question is how? I do have below approach on my mind: 1) Instead of a Link object use a array of size 2 one of which holds the item and other reference to the next one. But I don’t thing it is a good way of doing. Can some one please suggest a better approach for implementing Linked list using arrays?

The point of a linked list is to reap the benefits of not using an array so theres no point in attempting to implement such a thing.

«Instead of a Link object use a array of size 2 one of which holds the item and other reference to the next one.» — That is a way of somehow forcing an array into the solution. Don’t do that!

2 Answers 2

It’s called an ArrayList

Contrary to what @trutheality says, they don’t require a fixed capacity and the nodes don’t store an index to the next item. To get around the size constraints of a typical array, ArrayLists are designed to automatically resize when they reach a pre-defined min/max boundary.

Resizing the internal array is expensive. It includes creating a new array and moving the data from the old array to the new. As such, it’s beneficial to limit the number of resize operations needed.

One approach is to double the array size when the list reaches the max capacity, and shrink it by half when the list hits 1/4 capacity.

The reason an array isn’t shrunk at half capacity is to avoid thrashing. Thrashing, is when an array increases/decreases in size on the edge of the capacity boundary, causing a lot of resize operations with few changes the internal data.

Despite the expense of resizing — since it only happens when the dataset doubles — the actual performance cost is only O(log n). So, in insertion cost is linearithmic O(N log N) while retrieval is constant O(N).

There is one major weakness of ArrayLists. If you add/remove arbitrary items from the list the array contents will have to be shifted to accommodate the changes. An operation which costs linear O(N) time.

Even though the cost of changing arbitrary items in a traditional LinkedList is cheap (ie constant O(1) time), the operation requires a lookup to find the position in the chain which costs linear O(N) time. Unless you’re creating a Queue, where both ends of the list are being mutated frequently, using an ArrayList as a list foundation is probably the better choice.

Source: Currently taking an Algorithms course and just finished implementing both an ArrayList and a LinkedList from scratch.

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Create Array of Linked Lists in Java

In this article, we will look at how to Create an Array of Linked Lists in Java . We will look at ways to create an Array of Linked Lists or a List of Linked Lists in detail with working examples. Let us first have a quick peek into the concept of Linked Lists in Java.

Linked List in Java

A Linked List is a linear, dynamic Data Structure that stores homogenous data(data of the same type) following a sequence in non-contiguous memory locations. Each value in the List is represented as a Node that holds the reference to its next consecutive Node in a different memory location.

Example of Linked List:

In Java, the implementation of Linked List is defined in the LinkedList class in java.util package as part of the Collection framework introduced in Java 8.

Application of Array of Linked Lists

There is a crucial need to create an Array of Linked Lists, they have wide use in representing the relationship between the nodes and edges of Graph Data Structure.

Although an Adjacency List using ArrayList is preferred, we can represent the Adjacency matrix representation of a Graph using this Array of Linked Lists. Each index of the array gives us information about the nodes and the Linked List at each index row gives information about the connected edges to the respective node.

Example of Adjacency Matrix or List:

Here, each row starting index indicates the array index which holds a Linked List within itself. The Linked List shows the corresponding edges connected to each of the starting indexes in a connected and directed graph.

Create Array of Linked Lists in Java

Without further ado, we outline different ways to create an Array of Linked Lists in Java.

Using Object[] array of Linked Lists in Java

We can create an Array of Linked Lists by using the Object[] type array.

• We will create LinkedList objects and initialize each list with dummy values using the add() method.
• We will then create an Object class-type array and initialize the array with the lists.
• As the Object class is the direct parent to all Java classes, it will readily accept the Linked Lists as input.
• Then, we print each List in the Object[] array using the toString() method.

Note: The advantage of using Object[] arr is that it allows us to store Linked Lists having elements of any data type as the Object class is a parent to all classes.

Let us look at the implementation code.

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Array of Linked List in Java

1. Demonstrate the Linked List Array Using a Traditional Array in Java
2. Demonstrate the Linked List Array Using the Constructor in Java

A LinkedList is the sequential and linear data structure that stores elements in a defined order. The data structure is a part of the Collection interface and is present in the java.util package.

The linked list also has elements stored in the node part. Each node has a data part for element storage and the pointer to keep the address of the next node. The elements in the list are not present in contiguous memory locations.

Demonstrate the Linked List Array Using a Traditional Array in Java

Below is the code block that creates an array of linked lists using loops.

import java.util.LinkedList;  public class Main   public static void main(String[] args)   LinkedList[] list = new LinkedList[5];  for (int i = 0; i  5; i++)   if (list[i] == null)   list[i] = new LinkedList();  int temp = i;  for (int j = 0; j  temp + 1; j++)   list[i].add(j);  >  >  System.out.print(list[i]);  >  > > 

In the block above, the new LinkedList[5] statement creates a linked list. The new keyword calls the public constructor of the class linked list. The value 5 demonstrates the size of the array, so we create an array of 5 linked lists.

Over the list variable, the loop runs to instantiate a new linked list over each node. So a for loop gets applied with a condition of integer value less than 5 starts running. Internally, it checks the condition if the value in the node is null ; otherwise, a new linked list node instantiates.

Again, a for loop gets used to fill the elements in the list. The add method is used to append the elements at the end of the list. The method is from the LinkedList class and returns the boolean value. It returns true if the add function gets successfully done, else false .

Similarly, the iteration continues, and each node’s value gets filled with the linked list. The same is also printed inside the loop to check the elements present in the nodes.

[0][0, 1][0, 1, 2][0, 1, 2, 3][0, 1, 2, 3, 4] 

Demonstrate the Linked List Array Using the Constructor in Java

Below is the code block that uses Java 8 features and functions to create an array of linked lists.

import java.util.ArrayList; import java.util.LinkedList;  public class main    public static void main(String[] args)    LinkedList list1 = new LinkedListString>();  list1.add("l1_value1");  list1.add("l1_value2");   LinkedList list2 = new LinkedList();  list2.add("l2_value1");  list2.add("l2_value2");   LinkedList list3 = new LinkedList();  list3.add("l3_value1");  list3.add("l3_value2");   ArrayListLinkedList> arrayList = new ArrayListLinkedList>();  arrayList.add(list1);  arrayList.add(list2);  arrayList.add(list1);  arrayList.forEach(System.out::println);  System.out.println("Classname: " + arrayList.get(0).getClass());  > > 

In the code block above, the main method holds the actual logic for the code execution.

Firstly, a linked list is created using the new keyword. The keyword invokes the public constructor of the LinkedList class. The string values get inserted into the list. Similarly, another two lists are created.

Finally, an array list gets instantiated. The list variables formed are added in the array list instance. The iteration of the list instance happens using the forEach function. Additionally, a print statement with the method reference operator, :: , is added to show the name of instance type present in the array list.

The output of the program above is shown below.

[l1_value1, l1_value2] [l2_value1, l2_value2] [l1_value1, l1_value2] Classname: class java.util.LinkedList 

Rashmi is a professional Software Developer with hands on over varied tech stack. She has been working on Java, Springboot, Microservices, Typescript, MySQL, Graphql and more. She loves to spread knowledge via her writings. She is keen taking up new things and adopt in her career.

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Array of Linked Lists Java

I am trying to create an array of linked lists The program I am trying to write has a string array of names, however some names are in the same position of the array. For example if the name morgan is in array[0] and john is also in array[0] how can I create a linked list that allows both of the names to be stored in the same index. I am trying to replicate separate chaining collision resolution. Is it possible to use LinkedList inkedlist = new LinkedList(); If I use that how can I create a new linked list for each array index?

From what I understand. You don’t need to do much. Just keep adding the names to the list accessing the same array location. Suppose you have a name in arr[0]. Create a new node for the list at arr[0] and just add another name to that list accordingly.

2 Answers 2

I don’t know if I understand your question. Here is your question. you are trying to create an array of linked lists The program has ‘a string array’ of names,

: You have String name in the node if you add correctly, you will get the linkedlist.

however some names are in the ‘same position’ of the array. For example if the name morgan is in array[0] and john is also in array[0] how can I create a linked list that allows both of the names to be stored in the same index.

: How about adding one more Sting in the object, it that what you want?

Not sure if I started correctly but this is what I have so far

: You should start with a constructor first and make add, delete, and other functions.

public Class CustomList < private CustomList head; private int index = 0; private Class Node< private String firstName; private String secondName; private Node next; **constructor** public Node(String firstName, String secondName)< this.firstName = firstName; this.secondName = secondName; next = null; >> **constructor** public CustomList() < head = null; >> 

The above will contain two String values in the same index of CustomList. If I understood the question wrong or you have any more question feel free to ask.

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