The first step in constructing an exception handler is to enclose the
code that might throw an exception within a try
block.
In general, a try
block looks like the following:
try { code } catch and finally blocks . . .
The segment in the example labeled code
contains one
or more legal lines of code that could throw an exception. (The catch
and finally
blocks are explained in the next two subsections.)
To construct an exception handler for the writeList
method from the ListOfNumbers
class, enclose the exception-throwing
statements of the writeList
method within a try
block.
There is more than one way to do this. You can put each line of code that might
throw an exception within its own try
block and provide separate
exception handlers for each. Or, you can put all the writeList
code
within a single try
block and associate multiple handlers with it.
The following listing uses one try
block for the entire method
because the code in question is very short.
private List<Integer> list; private static final int SIZE = 10; PrintWriter out = null; try { System.out.println("Entered try statement"); out = new PrintWriter(new FileWriter("OutFile.txt")); for (int i = 0; i < SIZE; i++) { out.println("Value at: " + i + " = " + list.get(i)); } } catch and finally statements . . .
If an exception occurs within the try
block, that
exception is handled by an exception handler associated with it.
To associate an exception handler with a try
block,
you must put a catch
block after it; the next section,
The catch Blocks, shows you how.