Exceptions let you handle unusual error conditions without cluttering your code with nested ifs after every method call. You can use a single piece of code at a higher level to deal with all the exceptions triggered at a lower level. You can handle some of the exceptions at lower levels and others at a higher level and others you don’t handle at all, just let them terminate your program. 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.
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.
String trickyMethod() throws IOException { int result = readAnotherChar(); if ( result < 0 ) throw new IOException( "bad data" ); return result; }
Type codes used in describing Exceptions | ||||
---|---|---|---|---|
Letter | Type | Parent Class | Checked? (declare throws?) |
Use |
R | Runtime | java.lang.RuntimeException | Error that can occur in almost any code e.g. NullPointerException. | |
E | Error | java.lang.Error | Serious error you really should not try to catch, e.g. OutOfMemoryError. | |
C | Checked | java.lang.Exception | Likely exceptional condition that can only occur in specific places in the code e.g. EOFException. |
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 );
If the Exception is checked, you must either fob it off on the caller, with the throws clause or catch it yourself. Unchecked Exceptions are ones like running out of RAM (Random Access Memory) that, in general you can’t do much about, or that are not associated with specific problematic code, or that are very common such as IllegalArgumentException or NullPointerException. You don’t have to catch unchecked Exceptions or explicitly fob them off on the caller with throws. The classification of an Exception is not an exact science. It is a little bit like the arbitrary assignment of gender in French or German to objects. You just have to look it up. There is a major clue, Error Exceptions end in the string Error while checked Exceptions and RuntimeExceptions end in the string Exception.
Specific 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) (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 (Remote Method Invocation) 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 (Object Request Brokers) 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) (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 | Similar to ArrayIndexOutOfBoundsException for ArrayList. |
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 (End Of File) 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 allotted 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 | notes. |
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. |
recommend book⇒Java in a Nutshell | ||||
by | Benjamin J Evans, David Flanagan | 978-1-4493-7082-4 | paperback | |
---|---|---|---|---|
publisher | O’Reilly | 978-1-4493-7131-9 | eBook | |
published | 2014-11-06 | B00OL0853O | kindle | |
Greyed out stores probably do not have the item in stock. Try looking for it with a bookfinder. |
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