7.17: Here is a typical Java solution:

Transcription

1 7.17: Here is a typical Java solution: A job queue (of an operating system) is implemented as a two-way linked list. New items are added to the rear of the queue and old items are removed from the front of the queue. import java.io.*; import java.util.*; class JobRecord public int public JobRecord public JobRecord class JobRecord class JobQueue data members private JobRecord private JobRecord jobnumber; next; previous; front; rear; accessor methods public JobRecord getfront () return front; public JobRecord getrear () return rear; public void setfront (JobRecord newjob) front = newjob; public void setrear (JobRecord newjob) rear = newjob; methods public void initializejobqueue () initializejobqueue initializes front and rear pointers of queue setfront (null); setrear (null); initializejobqueue public void addjobtoqueue (int jobnumber) addjobtoqueue adds job to queue JobRecord newjob = new JobRecord ();

2 newjob.jobnumber = jobnumber; newjob.previous = rear; newjob.next = null; if (getfront () == null) setfront (newjob); else getrear ().next = newjob; setrear (newjob); addjobtoqueue public void removejobfromqueue () removejobfromqueue removes first item in queue setfront (getfront ().next); if (getfront () == null) setrear (null); else getfront ().previous = null; removejobfromqueue public void printjobqueue () printjobqueue prints items in job queue JobRecord temp; temp = getfront (); System.out.println ("The queue contains:"); while (temp!= null) System.out.println (temp.jobnumber); temp = temp.next; printjobqueue class JobQueue class JobQueueApp public static void main (String args[])

3 try int j; Scanner in = new Scanner(System.in); JobQueue jq = new JobQueue (); jq.initializejobqueue (); System.out.println ("Enter Job Number (non-positive to quit):"); j = in.nextint(); while (j > 0) jq.addjobtoqueue (j); System.out.println ("Job " + j + " entered."); System.out.println ("Enter Job Number (non-positive to quit):"); j = in.nextint(); jq.printjobqueue (); System.out.println ("Will remove top job from queue..."); jq.removejobfromqueue (); jq.printjobqueue (); catch (Exception e) System.out.println ("***** Error: JobQueueApp.main () *****"); System.out.println ("\t" + e); main class JobQueueApp

4 12.8: The following assumptions are made: there are no service charges, no ATM withdrawals. The only transactions that are allowed are checks and deposits. All checks bear a number. The user has a pile of canceled checks, and a pile of deposit slips. STATEMENT statement_details CHECKS check_details verify_ statement deposit_details DEPOSITS Figure Data flow diagram for determining whether bank statement is correct. Sort the checks in check-number order. For each check, find an entry in the bank statement that matches the check number. If no such entry is found, the statement is in error. Otherwise, mark that entry, and verify that the amount for that entry is the same as that on the check. If the amounts do not match, the statement is in error. Sort the deposit slips according to date of deposit. For each deposit slip, find an entry in the statement that matches the date of deposit and the amount of the deposit. Mark that entry. If no such entry is found, the statement is in error. After all checks and deposits have been processed, verify that all items on the statement have been marked. If not, the statement is in error. Add the amount of all deposits to the beginning balance, and from that sum subtract the total of all the checks. If the result of that subtraction is not equal to the ending balance then the statement is in error, otherwise it is correct. 12.9: See Figure : The FSM is shown in Figure Set of states is S0, S1, S2, S3, S4 Set of inputs is +,,., 0, 1 Initial state is S0 Set of final states is S4

5 Figure Finite state machine for accepting fixed-point binary numbers.

6 13.20: In this solution, subheadings are underlined. An extended scenario for the use case of Problem (Figure 11.9) appears in Figure Read the bank statement. 2. Read and sort the checks in check-number order. For each check, there is an entry found marked in the bank statement that matches the check number, and the amount for that entry is the same as that on the check. Mark the entry. 3. Read and sort the deposit slips according to date of deposit. For each deposit slip, there is an entry found in the statement that matches the date of deposit and the amount of the deposit. Mark the entry. 4. All items on the statement have been marked. 5. Add the amount of all deposits to the beginning balance, and from that sum subtract the total of all the checks. The result is equal to the ending balance. A. For at least one check, there is an entry in the bank statement that does not match the check number. B. For at least one check, there is an entry in the bank statement that matches the check number, but the amount for that entry is not the same as that on the check. C. For at least one deposit slip, there is an entry in the statement that does not match the date of the deposit. D. For at least one deposit slip, there is an entry in the statement that does not match the amount of the deposit. E. After all checks and deposits have been processed, one or more items on the statement have not been marked. F. Adding the total of all deposits to the beginning balance and then subtracting the total of all the checks does not yield the ending balance. Figure An extended scenario for the software product to determine whether a bank statement is correct. Candidate entity classes are determined using noun extraction. Description of software product in a single paragraph: A software product for determining whether a bank statement is correct is to be constructed. The data to be used are: the bank statement including the balance at the beginning of the month, the check and deposit entries and the balance at the end of the month; the number, date, and amount of each check; and the date and amount of each deposit.

7 Identify the nouns: A software product for determining whether a bank statement is correct is to be constructed. The data to be used are: the bank statement including the balance at the beginning of the month, the check and deposit entries and the balance at the end of the month; the number, date, and amount of each check; and the date and amount of each deposit.. With regard to the nouns in the previous paragraph, product, balance, data, and month are abstract nouns and are therefore unlikely to be classes. Also, number, date, and amount relate to the checks, date and amount relate to the deposits, and balance relates to the bank statement. This leaves Statement, Entry (Check Entry and Deposit Entry ), Check, and Deposit Slip as candidate entity classes. The initial class diagram is shown in Figure The initial statechart is shown in Figure The boundary class is Screen. The control class is Determine Correctness. Figure The initial class diagram for the software product to determine whether a bank statement is correct.

8 Matching Entries Read the bank statement Read. and sort the checks in check-number order Match checks with check statement entries Read and sort the deposit slips in date of deposit order. Match deposit slips with deposit statement entries Determining Whether Statement is Correct Determine whether the statement balances. Finishing Report whether the statement balances. Figure The initial statechart of the software product to determine whether a bank statement is correct. Statement Entry Account Holder Screen Determine Correctness Check Entry Deposit Entry Check Deposit Slip Figure The class diagram showing the classes that realize the use case of Figure 11.9.

9 The class diagram for the use case of Figure 11.9 (the only use case) is shown in Figure The communication diagram is shown in Figure 13.61, the flow of events in Figure 13.62, and the equivalent sequence diagram in Figure There is only one use case (Figure 11.9), so the final class diagram is the class diagram of Figure : Create entry 10: Find check match 16: Find deposit match 3: Create statement 9: Find check match 15: Find deposit match 19: Get balances :Statement 5: Return entry 11: Return matched 17: Return matched :Entry 1: Supply bank statement, check and deposit details 2: Transfer details 6: Return statement 12: Return matched 18: Return matched 20: Return balances Account Holder 22: Display confirmation of correctness :Screen 21: Send confirmation of correctness :Determine Correctness :Check Entry :Deposit Entry 8: Return check 7: Create check 14: Return deposit slip 13: Create deposit slip :Check :Deposit Slip Figure A communication diagram of the realization of the normal scenario of Figure of the use case of the software product to determine whether a bank statement is correct. The account holder supplies the bank statement, check and deposit slip details (1, 2). The product stores the statement details (3, 4). It then stores the check details (7, 8). For each check, it finds a check entry that matches the number and the amount (9 12). The product stores the deposit slip details (13, 14). For each deposit slip, it finds a deposit entry that matches the date and amount ( 15 18). The product now gets the beginning and end balances of the statement (19, 20), adds the amount of all deposits to the beginning balance, and from that sum subtracts the total of all the checks. The result is equal to the ending balance. The product displays a confirmation of correctness to the account holder (21, 22). Figure The flow of events of the realization of the scenario of Figure of the use case of the software product to determine whether a bank statement is correct.

10 Account : Screen : Determine : Statement Holder Correctness 1: Supply bank statement, check and deposit details 2: Transfer details 3: Create statement 4: Create entry : Entry : Check : Deposit Slip 6: Return entry 5: Return entry 7: Create check 8: Return check 9: Find check match 12:Return matched 10: Find check match 11: Return matched 13: Create deposit slip 14: Return deposit slip 15: Find deposit match 18: Return matched 19: Get balances 16: Find deposit match 17: Return matched 20: Return balances 22: Display confirmation of correctness 21: Send confirmation of correctness Figure A sequence diagram equivalent to the communication diagram of Figure The flow of events is therefore as shown in Figure

11 14.14: The final class diagram is shown in Figure Screen +getnumber() : string +getamount() : decimal +getdate() : Date +displayresult(in result : bool) : void Statement -startingbalance : decimal -endingbalance : decimal +getstartingbalance() : decimal +getendingbalance() : decimal +addentry(in entry : Entry ) : void +findmatch(in check : Check ) : bool +findmatch(in deposit : DepositSlip ) : bool 1 * DetermineCorrectness +determinecorrectness() : bool Entry -entrydate : Date -entryamount : decimal +match(in entry : Entry ) : bool CheckEntry -checknumber : string +getnumber() : string +match(in entry : Entry ) : bool Check -checknumber : string -checkdate : Date -checkamount : decimal +getchecknumber() : string +getdate() : Date +getamount() : decimal DepositEntry +match(in entry : Entry ) : bool DepositSlip -depositdate : Date -depositamount : decimal +getdate() : Date +getamount() : decimal Figure Final class diagram for the program to balance a checkbook. The detailed design of method determinecorrectness appears in Figure

12 Boolean determinecorrectness (void) get statement details and create statements get check details and create checks sort the checks by checknumber; for each check find an entry in the bank statement that matches checknumber; if (no such entry is found) return false; else mark that entry; verify that the amount for that entry is the same as that on the check; if (checkamount does not match) return false; get deposit slip details and create deposit slips sort the deposit slips by depositdate; for each deposit slip find an entry in bank statement that matches depositdate and depositamount; if (no such entry is found) return false; else mark that entry; verify that the amount for that entry is the same as that on the deposit slip; if (depositamount does not match) return false; if (all items on the statement have not been marked) return false; if (statement.startingbalance + sum (depositamount) sum (checkamount) == statement.endingbalance) return true; else return false; Figure The detailed design of method determinecorrectness.