5 Best Data Structures Every Java Programmer Should Know

Best Data Structures

The age of digitalization means there are large volumes of data being generated everyday. Businesses need to have a system to store, access and analyze this information to be able to make meaningful decisions. There is a felt need for a system that ensures that the processing speed, searchability, multiple requests are all accommodated effectively.  

What is a data structure?

Data structures store and organize data for operational purposes which is to access and update data efficiently. Data structures ensure the data items are traversed easily and also improve the efficiency of the program. 

The choice of data structures depend on the program and its needs. 

There are two kinds of data structure :

  1. Primitive Data structure– They can store only one type of information. Examples include integer, character, Boolean, float, double, long, etc.
  2. Non- Primitive Data Structure- Can store different types of data in a single entity.
    • Linear Data Structure– It is sequential in nature, all the elements in the memory are stored sequentially, e.g. include Array, Linked list, Stack, Queue.
    • Non-linear data Structure–  Non-linear data structure is a random type of data structure. Examples include Tree and Graph.

With the above information in mind, let us now look at the best data structures Java Programmers should know. 

Arrays In Java

A group of like-typed variables referred to by a common name is called an array in Java. Let’s look at some of the important points about Arrays in Java:

  • All arrays are allocated dynamically 
  • Arrays are stored in consecutive memory locations 
  • The length of the arrays can be detected using the object property length 
  • can be declared like other variables with [] after the data type
  • The variables are all indexed beginning from zero
  • can be used as a static field, a local variable, or a method parameter
  • The array size must be specified by int or short value and not long
  • Object is the direct superclass of an array type 
  • Every array type implements the interfaces Cloneable and java.io.Serializable
  • Supports random access
  • Size of the array can’t be altered once initialized but an array reference can be made to point to another array

Below is an example of a Java array.

Trees In Java

Tree in Java is a popular data structure which is nonlinear in nature and unlike other data structures like array, stack, queue, and linked list, it is hierarchical in nature. A tree has nodes and 2 pointers, the left child and the right child of the parent node respectively. 

Let’s try understanding the tree in details:

Root– Top most node of the tree which has no parent node, every tree has just one root node

Edge– The link between the parent node and the child node

Leaf– A node with no child is called a leaf node, there can be multiple leaf nodes in a tree

Subtree– The subtree of a node is the tree considering that particular node as the root node

Depth– The distance between a particular node and the root node is called depth

Height– The distance between a particular node and the deepest node of that subtree

Height of tree– The maximum height of any node which is same as the height of the root node 

Stacks in Java

The Stack Class of Java Collection Framework, models and implements a Stack Data Structure, which is a linear data structure which follows a specific order in which operations are performed. The order can be LIFO(Last In First Out) or FILO(First In Last Out). 

A wonderful example to explain it could be a stack of paper napkins, the ones on the top are pulled out first and the one at the bottom remain in the stack for the longest time and the last one out. 

The class provides not just push and pop operation but also provides empty, search and peek functions.

The Hierarchy of the Stack Class is depicted as below:

When the stack is empty, it uses EmptyStackException.

Queue in Java

Que Interface extends the collection interface in the java.util package and is primarily used for holding elements run in the First In First Out of FIFO order. It inserts elements at the end of the list and deletes elements at the beginning of the list. The Que requires a concrete class for declaration and the most common classes are LinkedList and PriorityQueue. For thread safe implementation PriorityBlockingQueue is the option. 

Linked lists In Java

Another important aspect of java.util pack’s collection framework and class is another implementation of the LinkedList data structure. It is a linear data structure where elements are not stored in adjacent locations but every element is a separate object with data parts and joined by addresses and pointers and each of these elements are referred to as nodes. LinkedLists are dynamic in the sense that insertions and deletions are easy to carry out. And therefore they are preferred more than arrays.


Data structures are the foundation of the computing process and therefore a sound understanding of the programming language and data structures ensure that one is able to code well, handle data and execute algorithms to solve coding problems. 

If you want to learn software development,  web development or build a career in data sciences, you must have a solid foundation in data structures. 

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