Objective $1$: Reading Items into a Data StructureThe first objective is to read an input file items.txt$,$ which contains data about what items are available for purchase. Figure $2$ shows an example of what this file may contain. You can create an instance of such a file for testing purposes. The actual formatting of the files uses a list of comma$-$separated values so you can easily read them line$-$by$-$line using Javas Scanner class. Once you have read the file, you should store the items in objects of a suitable custom class and add them to an appropriate data structure.The following requirements must be completed to get full marks for this objective: You should create a function called readItems$($filename$)$ that takes as input theitems.txt and adds items to a data structure. It does not need to return anything. Measure the running time for running this function. State the asymptotic worst$-$case time and space complexity of your function using Big$-$O notation. Objective $2$: Item InventoryThe second objective is to allow the user to manage and query the inventory. The following requirements must be completed to get full marks for this objective: You should create a function called addItem$($id$,$ name, stock, price$)$ that takes as input the attributes of a new item then adds a new item to your data structure. It returns true if the addition was successful and false otherwise.You should create a function called updateItemStock$($id$,$ newStock$)$ that takes as input the item ID and the new stock then updates the items stock accordingly. It returns true if the update was successful and false otherwise.You should create a function called getStock$($id$)$ that takes as input the item ID and returns the stock available for that item.All of the above functions must run in worst$-$case time O$($lg n$)$ or less, where n is the number of items.Measure the running time for all functions.Compare your running time of getStock to another function getStockFromArray where items are stored in a simple array instead of the data structure that you initially chose in Objective $1.$Objective $3$: Purchasing OperationsThe third objective is to allow the user to initiate and maintain purchases of items. The following requirements must be completed to get full marks for this objective:You should create a method called addNewPurchase$($arrayOfIds$)$ that accepts an array of items IDs and deducts one stock from each item specified in this area. For example if arrayOfIds $=[2,9,4]$ then it will remove one unit from the stock of item $2,$ item $9,$ and item $4.$ The method will return the total price for this purchase or an error if there is not enough stock for the selected items.You should create a method called undoLastPurchase$($k$)$ that undoes the last k pur$-$ chases. The stocks if those items need to be reverted back to their original values.Objective $4$: Most Profitable ItemThe fourth objective should allow the user to find the purchase that yielded the highest value $($defined as the total price of all items in that purchase$).$ For example, Figure $3$ shows some purchases that can be made by the user using the items from Figure $2.$ The highest priced purchase would be Purchase $3$ in this case. You should create a function called highestPriced$()$ that returns ID of the purchase with the highest total price. The above function must run in worst$-$case time O$($lgn$)$ or better, where n is the number of customers. Measure the running time of your function.