• A class in simpleIO package provided with our textbook.

• Allows you to write data to a file.

• Constructors:
  • SimpleWriter(String filename) - creates a SimpleWriter object that opens filename for output.
    If a file named filename already exists, it is overwritten.
  • SimpleWriter(String filename, boolean append) - creates a SimpleWriter object that opens filename for output.
    If a file named filename already exists and append is true, the new output is appended to the file.

• Methods:
  • putData(String s) writes s's value on a separate line in the file.
  • putData(char c) writes c's value on a separate line in the file.
  • putData(int x) writes x's value on a separate line in the file.
  • putData(double d) writes d's value on a separate line in the file.
  • putData(boolean b) writes b's value on a separate line in the file.
  • close() closes the file, saving its contents.

• Example: Write all of the values of the array myValues to the file "myoutput.dat".

      SimpleWriter outFile = new SimpleWriter("myoutput.dat"); 
      for (int i = 0; i < myValues.length; i++) {
          outFile.putData(myValues[i]);
      }
      outFile.close();
  

• A class in simpleIO package provided with our textbook.

• Allows you to read data from a file.

• Constructor:
  • SimpleReader(String filename) - creates a SimpleReader object that opens filename for input.
    

• Methods:
  • getString() returns a String read from the file.
  • getChar() returns a char value read from the file.
  • getInt() returns an int value read from the file.
  • getDouble() returns a double value read from the file.
  • getBoolean() returns a boolean value read from the file.
  • EOF() returns true if the end of the file as been reached.
  • close() closes the file.

• Example: Create an array called xValues to hold 10 integer values. Read in the values from the disk file called "myinput.dat".

       SimpleReader infile = new SimpleReader("myinput.dat");
       int [] xValues = new int[10];
       for (int i = 0; i < xValues.length; i++) {
           xValues[i] = infile.getInt();
       }
       infile.close();
  

• When an error condition occurs, Java provides a mechanism for sending an error message.
• This mechanism is called throwing an exception.
• You can detect (catch) this error indication by enclosing the code that generated in the exception in a try-catchblock:

      try {
           // stuff that might cause an error
      } catch (ExceptionName1 e) {
           // what you are going to do about the error from this exception
      } catch (ExceptionName2 e) {
           // what you are going to do about the error from this exception
      } 
  

try {
    SimpleWriter outFile = new SimpleWriter("myoutput.dat");
    for (int i = 0; i < myValues.length; i++) {
        outFile.putData(myValues[i]);
    }
    outFile.close();
} catch (FileNotFoundException e) {
    System.err.println("Can't open file " + e.toString());
} catch (IOException e) {
    System.err.println("I/O error " + e.toString());
    e.printStackTrace();
}

try {
     SimpleReader infile = new SimpleReader("myinput.dat");
     int [] xValues = new int[10];
     for (int i = 0; i < xValues.length; i++) {
         xValues[i] = infile.getInt();
     }
     infile.close();
} catch (FileNotFoundException e) {
    System.err.println("Can't open file " + e.toString());
} catch (IOException e) { 
    System.err.println("I/O error " + e.toString()); 
    e.printStackTrace(); 
} 

import simpleIO.*;
import java.io.*;