LinkedLists | sample app written using MVVM architecture | JSON Processing library

I have wrote the code which finds the merge point of two linkedLists, But in most test cases hackerrank throws run time error, I just wanted to know what causes it. Here is my code below:

I managed to find python code that defines a LinkedList class and all the defacto methods in it but quite can't figure out what each line of code does...Can someone comment on it explaining what each line does so i can grasp a better understanding of LinkedLists in python?

JAVA. I am trying to create a LinkedListStack to solve a mathematical expression. Ex: (1 + 2) * 4 - 3. I am having trouble with the different variable types saying that they are incompatible. There is an issue with the pop and peek methods I wrote and I cannot figure out how to get them to work. I cannot use the Java LinkedList or Stack classes, so I had to write the LLNode class and LinkedList class. Here are the errors I am getting:

I am new to Java and I finally faced with a problem that I have been postponing for a long time.

I was learning LinkedLists in Java and have the following confusion, please check:

I'm coding an implementation of HashTable as an exercise in my course, I'm using an array of LinkedLists, each containing a key-value pair (Element), to achieve this. Instead of writing list[key % size] to reference the element I'm manipulating, I want to write currentNode.

This code throws a NullPointerException:

I have 3 classes: Book,Student,LibrarySystem and i need 3 linkedlists to store data, first linkedList is called Node which stores Students, second linkedList is called studenBookNode which stores the books reserved by specific student and my third linkedList is allBooksNode which stores the created book objects here is my implementation below:

I am programming a 2D game in Java Swing. I have created several LinkedLists to hold instances of classes Tower, Entitiy and TowerBuildButtons. After I did this I realized that I want to have a superclass to all of these: Selectable. This is because all of these elements should have the capability to be selected and hovered over with the mouse. So I created the superclass Selectable and an additional LinkedList selectables.

The problem I am facing here is: When I add additional objects to the smaller lists (entities, towers, etc...) I also want them to be added to the larger selectables list. I can think of one solution to this. Creating a new add-method and making sure that when new objects are added, they are also added to selectables list. Example:

I'm a beginner coder trying to work on converter for words which should work that way:Input= "zero;six;eight;two" Output = "0682". But in my case the output I get is "0282". Are there any solutions to that? Or like maybe I should program differently?. I found that LinkedLists or HashMap could work, if so could you show how?

My Java program regarding Stacks made from LinkedLists. The task at hand was to merge two sorted stacks into one. I think I figured it out but it won't show any output and also it doesn't terminate. Can anyone help?

The "next" instance is pointing to the LinkedList's next element's address in the memory.