USF CS 110 - Strings and File I/O (11 pages)

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Strings and File I/O



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Strings and File I/O

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Pages:
11
School:
University of San Francisco
Course:
Cs 110 - Introduction To Computer Science I

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Strings and File I O Strings Java String objects are immutable Common methods include boolean equalsIgnoreCase String str String toLowerCase String substring int offset int endIndex String replace char oldChar char newChar int indexOf String str File Input Text Option 1 Scanner File Scans input from given File Input from file instead of System in keyboard Easy to scan ints doubles etc Option 2 BufferedReader FileReader BufferedReader allows you to read a line at a time instead of a character File Input Text Option 1 Scanner Scanner scan new Scanner new File myfile txt String s while scan hasNext acts like an iterator s scan nextLine Option 2 Buffered Reader BufferedReader in new BufferedReader new FileReader myfile txt s in readLine returns null when EOF reached while s null s in readLine in close remember to CLOSE the file Tips Scanner must be imported from java util File and Readers must be imported from java io Must deal with IOException Use try catch for file operations or declare throws IOException in method header public static void main String args throws IOException Exceptions An exception is an object that defines an unusual or erroneous situation Examples Divide by 0 Array index out of bounds File cannot be found Follow a null reference try catch try statements that may throw an exception catch Exception Type name what to do in case of exception Exception Type catch Another Type another name what to do in case of exception Another Type Propagation void divider throws ArithmeticException int a 5 int b 0 int c a b File Output Text FileWriter allows you to write to a file PrintWriter provides interface of System out Remember to import correct packages and handle exceptions PrintWriter out new PrintWriter new FileWriter myfile txt out println String 1 out println String 2 out close remember to CLOSE the file Misc Path names Relative path name starts looking in current directory Examples myfile txt mydirectory myfile txt Absolute path name starts from top level



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