EXCEPTION HANDLING AND TEXT I/O - Introduction to Java Programming: Comprehensive Version - page 461

try {
...
}
catch (Exception ex) {
...
}
catch (RuntimeException ex) {
...
}

try {
...
}
catch (RuntimeException ex) {
...
}
catch (Exception ex) {
...
}

(a) Wrong order (b) Correct order

Note
Java forces you to deal with checked exceptions. If a method declares a checked exception
(i.e., an exception other than Error or RuntimeException ), you must invoke it in a
try-catch block or declare to throw the exception in the calling method. For example,
suppose that method p1 invokes method p2 , and p2 may throw a checked exception
(e.g., IOException ); you have to write the code as shown in (a) or (b) below.

catch or declare checked
exceptions

void p1() {
try {
p2();
}
catch (IOException ex) {
...
}

void p1() throws IOException {

p2();

}

}

(a) Catch exception (b) Throw exception

Note
You can use the new JDK 7 multi-catch feature to simplify coding for the exceptions
with the same handling code. The syntax is:

JDK 7 multi-catch

catch (Exception1 | Exception2 | ... | Exceptionk ex) {
// Same code for handling these exceptions

}

Each exception type is separated from the next with a vertical bar ( | ). If one of the
exceptions is caught, the handling code is executed.

12.4.4 Getting Information from Exceptions
An exception object contains valuable information about the exception. You may use the fol-
lowing instance methods in the java.lang.Throwable class to get information regarding
the exception, as shown in Figure 12.4. The printStackTrace() method prints stack trace

methods in Throwable

java.lang.Throwable

+getMessage(): String
+toString(): String

Returns the message that describes this exception object.
Returns the concatenation of three strings: (1) the full name of the exception
class; (2) ":" (a colon and a space); (3) the getMessage() method.
Prints the Throwable object and its call stack trace information on the
console.
Returns an array of stack trace elements representing the stack trace
pertaining to this exception object.

+printStackTrace(): void

+getStackTrace():
StackTraceElement[]

F IGURE 12.4

Throwable is the root class for all exception objects.