Java 天地·Core Java·Lecture Notes·Unit 10 - Applications, File Handling and Exceptions

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Throwing an exception

The previous section explained how to define a new exception, called NotTextFileException. This exception was to be thrown by the method openTextFile() if the user tried to open a file that was not a text file. Here is how the exception is thrown:

throw (new NotTextFileException());

Note that it is a specific object of the class that is thrown, not the class itself. So we use new to create the exception object, and throw to throw the new exception.

A program can throw any exception, not just the ones it defines. However, this is usually not useful; the built-in exceptions are thrown by the methods in the built-in classes.

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