A digitаl pаyment system keeps trаck оf transactiоns made by custоmers at a store’s point of sale (for example, the cashier). Each transaction is either a purchase, which increases the amount in the store’s account balance, or a refund, which decreases the amount in the store’s account balance. Information about each transaction is stored using the following Transaction class. A Transaction object stores a unique identifier for the transaction (an id), a purchase indicator, and a value in pennies. A partial declaration for the Transaction class is shown below. public class Transaction { /** Returns a unique identifier for this transaction */ public String getId() { /* implementation not shown */ } /** Returns true if the transaction is a purchase, false if it is a refund */ public boolean isPurchase() { /* implementation not shown */ } /** Returns the amount of this transaction, represented as a positive number of whole pennies */ public int getPennies() { /* implementation not shown */ } // There may be instance variables, constructors, and methods not shown. } Batches of transactions, sorted in ascending id order, are processed using a Register class. The declaration of the Register class is shown below. public class Register { // Precondition: payments is sorted in ascending id order private Transaction[] payments; /** Calculates the net effect of some transactions on the store's account balance, as described in part (a). Precondition: ids is not null */ public int calculateDelta(String[] ids) { /* to be implemented in part (a) */ } /** Changes payments to include a batch of new transactions, as described in part (b). Precondition: entries is not null, is sorted in ascending id order, and all id values are either before or after those in payments */ public void addBatch(Transaction[] entries) { /* to be implemented in part (b) */ } // There may be instance variables, constructors, and methods not shown. } Write the Register method calculateDelta, which takes one parameter, an array of String values called ids. The method finds all the Transaction records in the payments instance variable which have id values (found using the getId method) matching the values in ids. It then calculates the net effect of their payment amounts (using the getPennies method) and returns the net effect in whole dollars that these transactions made to the account balance for the store, rounded to the nearest whole dollar. Id values not found in payments are ignored. The following example shows data from a set of transactions which could be stored in payments. Recall that each object stores an id, a purchase indicator, and a value in pennies. "A" "B" "C" "D" "E" "F" true true false true true true 899 1000 550 257 425 937 The following table shows the return values and explanation for some calls to the calculateDelta method, given the above data in payments. Input array provided to ids parameter Return value Explanation ["D","E","F"] 16 $2.57 + $4.25 + $9.37 = $16.19, rounded down to $16 ["D","C","B"] 7 $2.57 - $5.50 + $10.00 = $7.07, rounded down to $7 ["B","A"] 19 $10.00 + $8.99 = $18.99, rounded up to $19 ["B","ZZZ","A"] 19 $10.00 + $8.99 = $18.99, rounded up to $19 (no entry found with id "ZZZ") ["E","F","D","C"] 11 $4.25 + $9.37 + $2.57 - $5.50 = $10.69, rounded up to $11 Complete the calculateDelta method. /** Calculates the net effect of some transactions on the store's account balance, as described in part (a). Precondition: ids is not null */ public int calculateDelta(String[] ids)
Anаlyzing stаkehоlders in reаdings helps students understand what they read оn a deeper level and prоvides them with groups of people to discuss specifically in their writing.