Java Glossary : exception handling

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exception handling

Exceptions let you handle unusual error conditions without cluttering your code with nested ifs after every method call. There are two kinds of Exceptions, checked and unchecked. You don't need to declare unchecked Exceptions, those that derive from java.lang.Error and java.lang.RuntimeException, in your throws clauses. Checked Exceptions usually derive from java.lang.Exception. The basic syntax to handle an Exception looks like this:

String myMethod()
   {
   try
      {
      return trickyMethod();
      }
   catch ( IOException e )
      {
      return null;
      }
   }

The basic Syntax to generate an exception looks like this:

String trickyMethod() throws IOException
{
   int result = readAnotherChar();
   if ( result < 0 ) throw new IOException( "bad data" );
   return result;
}

For unchecked Exceptions ( i.e. Errors and RuntimeExceptions such as IllegalArgumentException) the throws clause is optional. I find them useful documentation since they show up in the JavaDoc.

Type codes used in describing Exceptions
Letter	Type	Parent Class	Checked? (declare throws?)	Use
R	Runtime	java.lang.RuntimeException	No	Error that can occur in almost any code e.g. nullPointerException.
E	Error	java.lang.Error	No	Serious error you really should not try to catch, e.g. OutOfMemoryError.
C	Checked	java.lang.Exception	Yes	Likely exceptional condition that can only occur in specific places in the code e.g. EOFException.

Collectively, RuntimeException, Error and Exception are derived from Throwable. RuntimeException is derived from Exception, which is derived from Throwable. Error is derived directly from Throwable.

If you catch RuntimeException you will catch all manner of run time exceptions (type R).
If you catch Error you will catch all manner of errors (type E).
If you catch Exception you will catch all manner of checked exceptions and run time exceptions (type R+C).
If you catch Throwable, you will catch everything, (Type R+E+C );

Exceptions
Exception Name	Type	Package	Notes
AbstractMethodError	E	java.lang
AccessControlException	R	java.security	This is an exception that is thrown whenever a reference is made to a non-existent ACL (Access Control List). notes.
AccessException	C	java.rmi	Thrown by certain methods of the java.rmi.Naming class.
AclNotFoundException	C	java.security.acl	Thrown whenever a reference is made to a non-existent ACL (Access Control List).
ActivateFailedException	C	java.rmi.activation	thrown by the RMI runtime when activation fails during a remote call to an activatable object.
ActivationException	C	java.rmi.activation
AlreadyBoundException	C	javax.naming
ApplicationException	C	org.omg.CORBA.portable	Used for reporting application level exceptions between ORBs and stubs
ArithmeticException	R	java.lang	Most commonly a divide by zero. notes.
ArrayIndexOutOfBoundsException	R	java.lang	Can be handled more generically with IndexOutOfBoundsException. notes.
ArrayStoreException	R	java.lang	Thrown to indicate that an attempt has been made to store the wrong type of object into an array of objects. notes.
AttributeInUseException	C	javax.naming.directory
AttributeModificationException	C	javax.naming.directory
AuthenticationException	C	javax.naming
AuthenticationNotSupportedException	C	javax.naming
AWTError	E	java.awt
AWTError	E	java/awt
AWTException	C	java.awt
BadLocationException	C	javax.swing.text	This exception is to report bad locations within a document model.
BatchUpdateException	C	java.sql
BindException	C	java.net	Signals that an error occurred while attempting to bind a socket to a local address and port
CannotProceedException	C	javax.naming
CannotRedoException	R	javax.swing.undo
CannotUndoException	R	javax.swing.undo
CertificateEncodingException	C	java.security.cert
CertificateException	C	java.security.cert
CertificateExpiredException	C	java.security.cert
CertificateNotYetValidException	C	java.security.cert
CertificateParsingException	C	java.security.cert
ChangedCharSetException	C	javax.swing.text
CharConversionException	C	java.io
ClassCastException	R	java.lang	notes.
ClassCircularityError	E	java.lang
ClassFormatError	E	java.lang	notes.
ClassNotFoundException	C	java.lang	notes.
CloneNotSupportedException	C	java.lang
CMMException	R	java.awt.color
CommunicationException	C	javax.naming
ConcurrentModificationException	R	java.util	This exception may be thrown by methods that have detected concurrent modification of a backing object when such modification is not permissible. E.g. two threads modifying a hashMap simultaneously. notes.
ConfigurationException	C	javax.naming
ConnectException	C	java.rmi
ConnectIOException	C	java.rmi
ContextNotEmptyException	C	javax.naming
CRLException	C	java.security.cert	CRL (Certificate Revocation List) Exception.
DataFormatException	C	java.util.zip
DigestException	C	java.security
EmptyStackException	R	java.util	Thrown by methods in the Stack class to indicate that the stack is empty. Does not refer to the system stack.
EOFException	C	java.io	notes.
Error	E	java.lang	Catches any serious error such as OutOfMemoryError that you unlikely can recover from.
Exception	C	java.lang	generic. Catches any specify Exception plus general Runtime exceptions, but not Errors.
ExceptionInInitializerError	E	java.lang	notes.
ExceptionInInitializerError	E	java.lang
ExpandVetoException	C	javax.swing.tree
ExportException	C	java.rmi.server
FileNotFoundException	C	java.io
FontFormatException	C	java.awt
GeneralSecurityException	C	java.security
IllegalAccessError	E	java.lang	notes.
IllegalAccessException	C	java.lang	Thrown when an application tries to load in a class, but the currently executing method does not have access to the definition of the specified class, because the class is not public and in another package.
IllegalArgumentException	R	java.lang	Most common exception to reject a bad parameter to a method.
IllegalComponentStateException	R	java.awt
IllegalMonitorStateException	R	java.lang
IllegalPathStateException	R	java.awt.geom
IllegalStateException	R	java.lang	Signals that a method has been invoked at an illegal or inappropriate time.
IllegalThreadStateException	R	java.lang
ImagingOpException	R	java.awt.image
IncompatibleClassChangeError	E	java.lang	notes.
IndexOutOfBoundsException	R	java.lang
IndirectionException	R	org.omg.CORBA.portable
InstantiationError	E	java.lang
InstantiationException	C	java.lang
InsufficientResourcesException	C	javax.naming
InternalError	E	java.lang
InterruptedException	C	java.lang	Thrown when a thread is waiting, sleeping, or otherwise paused for a long time and another thread interrupts it using the interrupt method in class Thread.
InterruptedIOException	C	java.io
InterruptedNamingException	C	javax.naming
IntrospectionException	C	java.beans
InvalidAlgorithmParameterException	C	java.security	This is a GeneralSecurityException. See IllegalArgumentException.
InvalidAttributeIdentifierException	C	javax.naming.directory
InvalidAttributesException	C	javax.naming.directory
InvalidAttributeValueException	C	javax.naming.directory
InvalidClassException	C	java.io	notes.
InvalidDnDOperationException	R	java.awt.dnd
InvalidKeyException	C	java.security
InvalidKeySpecException	C	java.security.spec
InvalidMidiDataException	C	javax.sound.midi
InvalidNameException	C	javax.naming
InvalidObjectException	C	java.io
InvalidParameterException	R	java.security
InvalidParameterSpecException	C	java.security.spec
InvalidSearchControlsException	C	javax.naming.directory
InvalidSearchFilterException	C	javax.naming.directory
InvalidTransactionException	C	javax.transaction
InvocationTargetException	C	java.lang.reflect
IOException	C	java.io
JarException	C	java.util.jar
KeyException	C	java.security
KeyManagementException	C	java.security
KeyStoreException	C	java.security
LastOwnerException	C	java.security.acl
LdapReferralException	C	javax.naming.ldap
LimitExceededException	C	javax.naming
LineUnavailableException	C	javax.sound.sampled
LinkageError	E	java.lang
LinkException	C	javax.naming
LinkLoopException	C	javax.naming
MalformedLinkException	C	javax.naming
MalformedURLException	C	java.net
MarshalException	C	java.rmi
MidiUnavailableException	C	javax.sound.midi
MimeTypeParseException	C	java.awt.datatransfer
MissingResourceException	R	java.util
NameAlreadyBoundException	C	javax.naming
NameNotFoundException	C	javax.naming
NamingException	C	javax.naming
NamingSecurityException	C	javax.naming
NegativeArraySizeException	R	java.lang
NoClassDefFoundError	E	java.lang	notes.
NoInitialContextException	C	javax.naming
NoninvertibleTransformException	C	java.awt.geom
NoPermissionException	C	javax.naming
NoRouteToHostException	C	java.net
NoSuchAlgorithmException	C	java.security
NoSuchAttributeException	C	javax.naming.directory
NoSuchElementException	R	java.util
NoSuchFieldError	E	java.lang
NoSuchFieldException	C	java.lang
NoSuchMethodError	E	java.lang	notes.
NoSuchMethodException	C	java.lang
NoSuchObjectException	C	java.rmi
NoSuchProviderException	C	java.security	notes.
NotActiveException	C	java.io	Thrown when serialization or deserialization is not active
NotBoundException	C	java.rmi
NotContextException	C	javax.naming
NotOwnerException	C	java.security.acl
NotSerializableException	C	java.io	notes.
NullPointerException	R	java.lang	Actually a null reference exception. notes.
NumberFormatException	R	java.lang	Commonly thrown when a String is converted to internal binary numeric format. notes.
ObjectStreamException	C	java.io
OperationNotSupportedException	C	javax.naming
OptionalDataException	C	java.io	Unexpected data appeared in an ObjectInputStream trying to read an Object. Occurs when the stream contains primitive data instead of the object that is expected by readObject. The EOF flag in the exception is true indicating that no more primitive data is available. The count field contains the number of bytes available to read.
OutOfMemoryError	E	java.lang	By the time this happens it is almost too late. gc has already done what it could. Possibly some process has just started gobbling RAM, or perhaps the problem you are trying to solve is just too big for the size of the alloted virtual ram. You can control that with the java.exe command line switches.
ParseException	C	java.text
PartialResultException	C	javax.naming
PolicyError	E	org.omg.CORBA
PrinterAbortException	C	java.awt.print
PrinterException	C	java.awt.print
PrinterIOException	C	java.awt.print
PrivilegedActionException	C	java.security
ProfileDataException	R	java.awt.color
PropertyVetoException	C	java.beans
ProtocolException	C	java.net
ProviderException	R	java.security
RasterFormatException	R	java.awt.image
ReferralException	C	javax.naming
RemarshalException	C	org.omg.CORBA.portable
RemoteException	C	java.rmi
RMISecurityException	C	java.rmi
RuntimeException	R	java.lang	Error that can occur in almost any code e.g. nullPointerException. Use this when to catch general errors when no specific exception is being thrown.
SchemaViolationException	C	javax.naming.directory
SecurityException	R	java.lang
ServerCloneException	C	java.rmi.server
ServerError	E	java.rmi
ServerException	C	java.rmi
ServerNotActiveException	C	java.rmi.server
ServerRuntimeException	C	java.rmi
ServiceUnavailableException	C	javax.naming
SignatureException	C	java.security
SizeLimitExceededException	C	javax.naming
SkeletonMismatchException	C	java.rmi.server
SkeletonNotFoundException	C	java.rmi.server
SocketException	C	java.net
SocketSecurityException	C	java.rmi.server
SQLException	C	java.sql
StackOverflowError	E	java.lang	notes.
StreamCorruptedException	C	java.io	ObjectStream data are scrambled. notes.
StringIndexOutOfBoundsException	R	java.lang	Can be handled more generically with IndexOutOfBoundsException. notes.
StubNotFoundException	C	java.rmi
SyncFailedException	C	java.io
SystemException	R	org.omg.CORBA
TimeLimitExceededException	C	javax.naming
TooManyListenersException	C	java.util
TransactionRequiredException	C	javax.transaction
TransactionRolledbackException	C	javax.transaction
UndeclaredThrowableException	R	java.lang.reflect
UnexpectedException	R	java.rmi
UnknownError	E	java.lang
UnknownException	R	org.omg.CORBA.portable
UnknownGroupException	C	java.rmi.activation
UnknownHostException	C	java.rmi
UnknownHostException	C	java.net
UnknownObjectException	C	java.rmi.activation
UnknownServiceException	C	java.net
UnknownUserException	C	org.omg.CORBA
UnmarshalException	C	java.rmi	notes.
UnrecoverableKeyException	C	java.security
UnsatisfiedLinkError	E	java.lang	notes.
UnsupportedAudioFileException	C	javax.sound.sampled
UnsupportedClassVersionError	E	java.lang
UnsupportedDataTypeException	C	java.io	undocumented. notes.
UnsupportedEncodingException	C	java.io
UnsupportedFlavorException	C	java.awt.datatransfer
UnsupportedLookAndFeelException	C	javax.swing
UnsupportedOperationException	R	java.lang	Use for code not yet implemented, or that you deliberately did not implement.
UserException	C	org.omg.CORBA
UTFDataFormatException	C	java.io
VerifyError	E	java.lang	notes.
VirtualMachineError	E	java.lang
WriteAbortedException	C	java.io
ZipException	C	java.util.zip	notes.

Missing BadDataFormatException

There is no BadDataFormatException to complain about badly formatted data files. You would expect there to be one either derived from IllegalArgumentException like NumberFormatException or from IOException like UTFDataFormatException. You can either reuse IllegalArgumentException or IOException, or roll your own BadDataFormatException.

Rolling Your Own Exception

Rolling your own Exception is easy:

import java.io.IOException;

/**
 * Thrown when stream format from server is out of spec.
 *
 * @author Roedy Green
 * @version 1.0 2003-07-27
 */
public class BadStreamException extends IOException
   {
   /**
   * Create a BadStreamExecption and list a reason why thrown.
   *
   * @param reason String describing the reason for the exception.
   */
   public BadStreamException ( String reason )
      {
      super( reason );
      }
   /**
   * Create a BadStreamException and list no reason why thrown.
   */
   public BadStreamException()
      {
      super();
      }
   }

Learning More

Peter Haggar has written a most excellent tutorial on exceptions.

Java in a Nutshell : A Desktop Quick Reference

1-56592-487-8

David Flanagan

Author of the classic Java In A Nutshell, now split into three different books Java in a Nutshell : The Desktop Quick Reference, The Java Foundation Classes and Java Examples in a Nutshell. The author answers his email and uses the feedback to improve the book. Ithas a comprehensive list of exceptions.

throw

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