Exceptions - Beginning Java - page 359

return array[index+2];
This statement is outside the try block, so the exception is not caught. The exception is therefore thrown
by the method when it is called in main() . However, you aren't obliged to declare that the divide()
method throws this exception because the ArrayIndexOutOfBoundsException class is a subclass of
RuntimeException and is therefore exempted from the obligation to deal with it.
The main() method has two try blocks. The first try block encloses three calls to the divide() method.
The first call executes without error; the second call causes an arithmetic exception in the method; and
the third call causes an index-out-of-bounds exception. There are two catch blocks for the first try block
in main() to deal with these two potential exceptions.
The read() method in the second try block in main() can cause an I/O exception to be thrown. Because
this is one of the exceptions that the compiler checks for, you must either put the statement that calls the
read() method in a try block and have a catch block to deal with the exception or declare that main()
throws the IOException exception. If you don't do one or the other, the program does not compile.
Using the read() method in this way has the effect of pausing the program until the Enter key is pressed.
You look at read() , and other methods for I/O operations in the next four chapters. The IOException
class is in the package java.io , so you need the import statement for this class because you refer to it
in the catch block using its unqualified name. Of course, if you referred to it as java.io.IOException ,
you would not need to import the class name. Remember that only classes defined in java.lang are in-
cluded in your program automatically.
Normal Execution of a Method
The first line of output from the TryBlockTest example indicates that execution of the try block in main()
has begun. The next block of output from the example is the result of a straightforward execution of the
divide() method:
First try block in divide() entered
Code at end of first try block in divide()
finally block in divide()
result = 2
No exceptions occur in divide() , so no catch blocks are executed.
The code at the end of the divide() method, following the catch blocks, isn't executed because the
return statement in the try block ends the execution of the method. However, the finally block in di-
vide() is executed before the return to the calling method occurs. If you comment out the return statement
at the end of the divide() method's try block and run the example again, the code that follows the fi-
nally block is executed.
The sequence of execution when no exceptions occur is shown in Figure 7-3 .
FIGURE 7-3