How To Check If Linked List Contains Loop In Java? How To Find The Starting Node Of The Loop? where next node is null, the slow pointer will be pointing to the middle node of the linked list.Ģ. So, when fast pointer will point to the last node i.e. In each step, the fast pointer moves two nodes, while slow pointer just steps one node. In the two pointer approach, you have two pointers, fast and slow. If Interviewer says that you cannot loop twice and you just have to use one loop, then you can use the two pointer approach to solving this problem. You should clarify what does mean by one pass in this question. How To Find Middle Element Of A Singly Linked List In One Pass? * JUnit tests will be created to test this singly linked list.1. * A Simple linked list implementation in Java to demonstrate unit testing. Singly Linked List Implementation in Java /** By the way, here is a good example of how singly linked list look like : After that, we will write unit tests for this linked list class. In this JUnit tutorial, we will create a singly linked list with three methods isEmpty(), length() and append().Īs the name suggests isEmpty() will return true, if linked list is empty, length() will return a number of nodes in a linked list, and append() is used to append a node at tail. A linked list is said empty if it doesn't contain any node i.e. The first node of the linked list is called head and last node is called tail. linked list store data in the form of nodes, which contains data and reference to next node. Since we will implement a singly linked list, we will keep discussion limited with that. A singly-linked list allows you to traverse in one direction, mostly forward, while the doubly linked list allows you to traverse in both direction, forward, and backward. There is two kinds of linked list, singly and doubly linked list. An array needs contiguous memory, while the linked list doesn't need that.īasics of linked list data structure in Javaīefore writing an implementation of linked list data structure, let's revise some terminology. By the way, there is much difference between the linked list and array data structure, which is the subject of another blog post, but the main difference is in the way objects are stored. In this JUnit tutorial, we will implement a linked list in Java and we will write unit test cases for a linked list.įor those, who are not familiar with the linked list, it's one of the fundamental data structures to store objects, like an array, which is also used to store objects. Since it always helps to start smaller, this JUnit tutorial will present another simple JUnit example to show how to write unit tests in Java. What all this means is, you, a Java developer, must write unit tests. There is a good chance of you discovering that a particular field or method is exposing implementation detail, and should be abstracted in the public method. JUnit tests also help to organize code and evaluate encapsulation. Many times, while writing unit tests, I have discovered better names for my methods and refactored large methods into smaller ones. It's natural and I had experienced it myself that unit test, not only provides code coverage, but also present unique opportunities for code refactoring. Writing unit tests is one of the best programming practices along with code review. Fortunately, Java ecosystem has the luxury of great unit testing frameworks in form of JUnit and TestNG, and every Java developer should take advantage of this. IMHO, unit testing is the best development practice to improve code quality. Coming to back to writing a unit test, from time to time, I have said that a Java programmer must write unit tests. Though Java has LinkedList class, which is an implementation of the doubly linked list, its good to know how to implement singly linked list in Java, mostly to practice coding interview questions. In this article, we will learn two things, how to implement a linked list from scratch in Java and how to write a unit test using JUnit framework.
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