Two Ways to Store Data in a File Text format Binary format

Text Format Information stored as a sequence of characters Characters are stored as their ASCII equivalent - int value stored as ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ 5 bytes File is ‘readable’ by humans. Java classes ‘Reader’ and ‘Writer’ (and their subclasses) are for use with text files

Binary Format More compact and efficient int stored using binary representation: bytes Java classes I nputStream and OutputStream (and their subclasses) exist to read and write these types of files

To Read Text Data From a Disk File Create a FileReader object Use its read method to read a single character o returns the next char as an int o or the integer -1 at end of input Test for -1 to determine if a char was read Close the file when done

Code FileReader reader = new FileReader("input.txt"); int next = reader.read() ; char c; if (next != -1) c = (char)next();. reader.close().

Write a Character to Disk FileWriter writer = new FileWriter("output.txt"); char c =‘a'; writer.write(c); writer.close();

Reading Text Line by Line Create a BufferedReader object (pass a FileReader object to constructor) objects of type BufferedReader can group characters – ‘buffer’ them method readLine() available, to provide file data 1 line at a time (the method handles reading the characters from the FileReader for you) readLine() returns the next line of file (as a String), or null if none exists

//Reads first line from file named input.txt // line is expected to contain a double value FileReader reader = new FileReader("input.txt"); BufferedReader in = new BufferedReader(reader); String inputLine = in.readLine(); double x = Double.parseDouble(inputLine);

//Reads and all lines from file // and writes them to console import java.io; public class demo{ public static void main(String[] args)throws IOException{ FileReader reader = new FileReader("input.txt"); BufferedReader in = new BufferedReader(reader); String line = in.readLine(); While (line != null){ System.out.println(line); line = in.readLine(); } in.close(); }

Writing Strings to Text Files A PrintWriter object handlethe ‘unbuffering’ of data for output file writer Create PrintWriter object (pass FileWriter object to constructor) PrintWriter class provides ‘println’ method which accepts data and prints the String form (which it provids to FileWriter one char at a time) FileWriter writer = new FileWriter(“output.txt”) PrintWriter out = new PrintWriter(writer);

//use PrintWriter object to output data to file output.txt FileWriter writer = new FileWriter(“output.txt”) PrintWriter out = new PrintWriter(writer); out.println(29.95); out.println(new Rectangle(5,10,15,25)); out.println("Hello, World!");