EXCEPTION HANDLING AND TEXT I/O - Introduction to Java Programming: Comprehensive Version - page 456

ClassNotFoundException

ArithmeticException

IOException

Exception

NullPointerException

RuntimeException

IndexOutOfBoundsException

Many more classes

Throwable Object

IllegalArgumentException

LinkageError

Many more classes

Error

VirtualMachineError

Many more classes

F IGURE 12.1

Exceptions thrown are instances of the classes shown in this diagram, or of subclasses of one of these classes.

Note
The class names Error , Exception , and RuntimeException are somewhat con-
fusing. All three of these classes are exceptions, and all of the errors occur at runtime.

The Throwable class is the root of exception classes. All Java exception classes inherit
directly or indirectly from Throwable . You can create your own exception classes by extend-
ing Exception or a subclass of Exception .
The exception classes can be classified into three major types: system errors, exceptions,
and runtime exceptions.

System errors are thrown by the JVM and are represented in the Error class. The
Error class describes internal system errors, though such errors rarely occur. If one
does, there is little you can do beyond notifying the user and trying to terminate the
program gracefully. Examples of subclasses of Error are listed in Table 12.1.

system error

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T ABLE 12.1

Examples of Subclasses of Error

Class Reasons for Exception

LinkageError A class has some dependency on another class, but the latter class has

changed incompatibly after the compilation of the former class.

VirtualMachineError The JVM is broken or has run out of the resources it needs in order to

continue operating.

Exceptions are represented in the Exception class, which describes errors caused by
your program and by external circumstances. These errors can be caught and handled
by your program. Examples of subclasses of Exception are listed in Table 12.2.

exception

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T ABLE 12.2

Examples of Subclasses of Exception

Class Reasons for Exception

ClassNotFoundException Attempt to use a class that does not exist. This exception would occur, for example, if you tried to

run a nonexistent class using the java command, or if your program were composed of, say,
three class files, only two of which could be found.

IOException Related to input/output operations, such as invalid input, reading past the end of a file, and opening

a nonexistent file. Examples of subclasses of IOException are InterruptedIOException ,
EOFException (EOF is short for End of File), and FileNotFoundException .