Exceptions - Beginning Java - page 355

The doSomething() method in Figure 7-2 deals with exceptions of either type MyException1 or MyEx-
ception2 in the first catch block. The second catch block is executed for exceptions of type MyExcep-
tion3 . The method can also throw two other types of exceptions that are not caught within the method, and
these are identified in the throws clause that follows the parameter list for the method. The code in the fi-
nally block always gets executed, regardless of whether an exception is thrown or not.
In many cases, a method needs only a single try block followed by all the catch blocks for the excep-
tions that need to be processed in the method, perhaps followed by a finally block. Java, however, gives
you the flexibility to have as many try blocks as you want. This makes it possible for you to separate vari-
ous operations in a method by putting each of them in their own try block — an exception thrown as a
result of a problem with one operation does not prevent subsequent operations from being executed.
Execution Sequence
You saw how the sequence of execution proceeds with the simple case of a try block and a single catch
block. Let's explore the sequence in which code executes when you have the try - catch - finally combin-
ations of blocks, when different exceptions are thrown. This is easiest to comprehend by considering an ex-
ample. You can use the following code to create a range of exceptions and conditions.
TRY IT OUT: Execution Sequence of a try Block
It is convenient, in this example, to use an input statement to pause the program. The method you
use can throw an exception of a type defined in the java.io package. You start by importing the
java.io.IOException class name into the source file. Give the class that contains main() the name
TryBlockTest . You define another method, divide() , in this class that is called in main() . The overall
structure of the TryBlockTest class source file is: