java.lang Throwable

java.lang
Throwable

Declaration
public class Throwable
java.lang.Object
|
+--java.lang.Throwable
Direct Known Subclasses: Error, Exception
Description
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();
}
Since: JDK1.0, CLDC 1.0


Constructors
Throwable()
Throwable(String message)
Methods
String getMessage()
void printStackTrace()
String toString()

Methods inherited from class Object
equals(Object), getClass(), hashCode(), notify(), notifyAll(), wait(), wait(), wait()

Constructors
Throwable()
Declaration:
public Throwable()
Description:
Constructs a new Throwable with null as its error message string.
Throwable(String)
Declaration:
public Throwable(java.lang.String message)
Description:
Constructs a new Throwable with the specified error message.
Parameters:
message - the error message. The error message is saved for later retrieval by the getMessage()
method.
Methods
getMessage()
Declaration:
public java.lang.String getMessage()
Description:
Returns the error message string of this Throwable object.
Returns: the error message string of this Throwable object if it was created with an error message
string; or null if it was created with no error message.
toString()
Declaration:
public java.lang.String toString()
Description:
Returns a short description of this Throwable object. If this Throwable object was created with an
error message string, then the result is the concatenation of three strings:
• The name of the actual class of this object
• “: ” (a colon and a space)



• The result of the getMessage() method for this object
If this Throwable object was created with no error message string, then the name of the actual class of
this object is returned.
Overrides: toString in class Object
Returns: a string representation of this Throwable.
printStackTrace()
Declaration:
public void printStackTrace()
Description:
Prints this 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.