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java.lang.Objectjava.lang.Throwable
@TransactionType(value=NOT_SUPPORTED) public class Throwable
The Throwable
class is the superclass of all errors and
exceptions in the Java language. Only objects that are instances of this
class (or of one of its subclasses) are thrown by the Java Virtual Machine or
can be thrown by the Java throw
statement. Similarly, only
this class or one of its subclasses can be the argument type in a
catch
clause.
Instances of two subclasses, Error
and
Exception
, are conventionally used to indicate that
exceptional situations have occurred. Typically, these instances are freshly
created in the context of the exceptional situation so as to include relevant
information (such as stack trace data).
By convention, class Throwable
and its subclasses have two
constructors, one that takes no arguments and one that takes a
String
argument that can be used to produce an error message.
A Throwable
class contains a snapshot of the execution stack
of its thread at the time it was created. It can also contain a message
string that gives more information about the error.
Here is one example of catching an exception:
try { int a[] = new int[2]; int b = a[4]; } catch (ArrayIndexOutOfBoundsException e) { System.out.println("exception: " + e.getMessage()); e.printStackTrace(); }
Direct instances of this class are not bound to any context and can be
passed between contexts without any restrictions. Objects created and returned
by the methods of this class are owned by the caller. In particular, a call to the getMessage()
returns a String instance bound to the owner context of the caller.
See Runtime Environment Specification for the Java Card Platform, Connected Edition, chapter 7 for details regarding transfer of ownership.
Constructor Summary | |
---|---|
Throwable()
Constructs a new Throwable with null as its
error message string. |
|
Throwable(String message)
Constructs a new Throwable with the specified error
message. |
Method Summary | |
---|---|
String |
getMessage()
Returns the error message string of this Throwable object. |
void |
printStackTrace()
Prints this Throwable and its backtrace to the standard
error stream. |
String |
toString()
Returns a short description of this Throwable object. |
Methods inherited from class java.lang.Object |
---|
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
public Throwable()
Throwable
with null
as its
error message string.
public Throwable(String message)
Throwable
with the specified error
message.
message
- the error message. The error message is saved for later
retrieval by the getMessage()
method.Method Detail |
---|
public String getMessage()
Throwable
object.
Throwable
object
if it was created
with an error
message string; or null
if it was
created
with no error message.public String toString()
Throwable
object. If
this Throwable
object was
created
with an error message string, then the
result is the concatenation of three strings:
getMessage()
method for this object
Throwable
object was created
with no error message string, then the name of the actual class of this
object is returned.
toString
in class Object
Throwable
.public void printStackTrace()
Throwable
and its backtrace to the standard
error stream. This method prints a stack trace for this
Throwable
object on the error output stream that is the
value of the field System.err
. The first line of output
contains the result of the toString()
method for this object.
The format of the backtrace information depends on the implementation.
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