File IO

• Input data may be read from the keyboard and file
• Output may be displayed on the output screen
• Output may be written in a file
• In Java, there are classes that supports input and/or output through input and output files
• Some classes for file input/output (FileIO) are defined in the java.io package.
• Programs that use the classes must have the import java.io.* statement.

  • BufferedReader
  • InputStreamReader
  • PrintWriter
  • OutputStream
• Reading input data through the keyboard may be allowed by using the BufferedReader class.
• Sometimes, you want to add the program output to the end of an existing text file.

  This process is called appending to a file.
• To be able to append, create an object of the PrintWriter class and connect it to the text file as shown below. 


  Notice the use of the “true” boolean expression.
• The Scanner class that is in the java.util.Scanner; package may also be used for reading/writing data from/to files.

  Hence, import java.util.Scanner; must be in the program.