Problem 1
Fill in the blanks in each of the following statements: a) Ultimately, all data items processed by a computer are reduced to combinations of ________ and _________ b) The smallest data item a computer can process is called a(n) ____________ c) \(A(n)\) ___________ can sometimes be viewed as a group of related records. d) Digits, letters and special symbols are referred to as _________ e) A database is a group of related ___________ f) Object _____________ normally enables a program to output error messages to the screen.
Problem 2
Determine which of the following statements are true and which are false. If \(f a l\) se, explain why. a) The programmer must explicitly create the stream objects System. in, System. out and System .err. b) When reading data from a file using class Scanner, if the programmer wishes to read data in the file multiple times, the file must be closed and reopened to read from the beginning of the file. This moves the file-position pointer back to the beginning of the file. c) Method exists of class File returns true if the name specified as the argument to the File constructor is a file or directory in the specified path. d) Binary files are human readable. e) An absolute path contains all the directories, starting with the root directory, that lead to a specific file or directory. f) Class Formatter contains method printf, which enables formatted data to be output to the screen or to a file.
Problem 4
Complete the following tasks, assuming that each applies to the same program: a) Write a statement that opens file "oldmast.ser" for input-use objectInputstream variable in01dMaster to wrap a FileInputStream object. b) Write a statement that opens file "trans.ser" for input-use ObjectInputStream variable inTransaction to wrap a FileInputStream object. c) Write a statement that opens file "newmast.ser" for output (and creation)-use \(0 \mathrm{b}-\) ject0utputStream variable outNewMaster to wrap a File0utputStream. d) Write a statement that reads a record from the file "oldmast.ser". The record is an object of class AccountRecordSerializable- use ObjectInputStream variable in01dMaster. Assume class AccountRecordSerializable is the same as the AccountRecordSerializable class in Fig. 14.17 e) Write a statement that reads a record from the file "trans.ser". The record is an object of class TransactionRecord - use ObjectInputStream variable inTransaction. f) Write a statement that outputs a record to the file "newmast.ser". The record is an object of type AccountRecordSerializable-use Object0utputStream variable outNewMaster.
Problem 5
Find the error in each block of code and show how to correct it. a) Assume that account, company and amount are declared. Object0utputStream outputStream; outputStream.writeInt( account ); outputStream.writeChars( company ); outputStream.writeDouble ( amount ); b) The following statements should read a record from the file "payables.txt". The Scanner variable inPayable should be used to refer to this file. Scanner inPayable = new Scanner( new File( "payables.txt" ) ); PayablesRecord record = ( PayablesRecord ) inPayable.readobject();
Problem 6
Fill in the blanks in each of the following statements: a) Computers store large amounts of data on secondary storage devices as __________ b) \(A(n)\) ____________ is composed of several fields. c) To facilitate the retrieval of specific records from a file, one field in each record is chosen as a \((n)\) ____________ d) Files that are created using byte-based streams are referred to as _________ files, while files created using character-based streams are referred to as ___________ files. e) The standard stream objects are __________, _________ and ____________
Problem 7
Determine which of the following statements are true and which are false. If false, explain why. a) The impressive functions performed by computers essentially involve the manipulation of zeros and ones. b) People specify programs and data items as characters. Computers then manipulate and process these characters as groups of zeros and ones. c) Data items represented in computers form a data hierarchy in which data items become larger and more complex as we progress from fields to characters to bits and so on. d) A record key identifies a record as belonging to a particular field. companies store all their information in a single file to facilitate computer processing of the information. When a program creates a file, the file is retained by the computer for future reference.
Problem 11
(Telephone-Number Word Generator) Standard telephone keypads contain the digits zero through nine. The numbers two through nine each have three letters associated with them (Fig. 14.27 ). Many people find it difficult to memorize phone numbers, so they use the correspondence between digits and letters to develop seven-letter words that correspond to their phone numbers. For example, a person whose telephone number is \(686-2377\) might use the correspondence indicated in Fig. 14.27 to develop the seven-letter word "NUMBERS." Every seven-letter word corresponds to exactly one seven-digit telephone number. A restaurant wishing to increase its takeout business could surely do so with the number \(825-3688\) (i.e., "TAKEOUT"). Every seven-letter phone number corresponds to many different seven-letter words. Unfortunately, most of these words represent unrecognizable juxtapositions of letters. It is possible, however, that the owner of a barbershop would be pleased to know that the shop's telephone number, \(424-7288,\) corresponds to "HAIRCUT." The owner of a liquor store would, no doubt, be delighted to find that the store's number, \(233-7226,\) corresponds to "BEERCAN." A veterinarian with the phone number \(738-2273\) would be pleased to know that the number corresponds to the letters "PETCARE." An automotive dealership would be pleased to know that the dealership number, \(639-2277,\) corresponds to "NEWCARS." Write a program that, given a seven-digit number, uses a Printstream object to write to a file every possible seven-letter word combination corresponding to that number. There are \(2,187\left(3^{7}\right)\) such combinations. Avoid phone numbers with the digits 0 and 1
