Chapter 11: Input/Output and Exception Handling

Reading Text Files

• Scanner in = new Scanner (new FileReader ("input.txt"));

Writing Text Files

• PrintWriter out = new PrintWriter("output.txt");

Closing Files

• in.close();
• out.close();

Exceptions

• Figure 1 on page 434 shows an inheritance hierarchy of exception classes.
• If you want to report an exception, use the throw command
  • throw new IllegalArgumentException();
• Unchecked exceptions extend the RuntimeException class or Error class. Unchecked exceptions arise due to programmer error. For example, dividing by 0.
• Checked exceptions are everything else in the Figure 1 inheritance hierarchy. Checked exceptions are due to external circumstances that the programmer cannot prevent. For example, the program is reading information across the internet and the network connection goes down.
• To show that a method can throw an Exception use the throws command
  • public void read (String filename) throws FileNotFoundException { ... }

Lecture Code

Note: For the code below to work, a file named lab10.htm must exist in the same directory as Demo.java.

• Demo.java