Flow Control - SCJP Sun Certified Programmer for Java Platform SE6 - page 232

Checked exceptions An exception is referred to as a checked exception if its data type is a
child class of java.lang.Exception , but not a child class of RuntimeException .
Errors An exception is referred to as an error if its data type is a child class of java
.lang.Error . An error is associated with problems that arise outside of your application,
and you typically do not attempt to recover from errors.
Figure 3.11 shows the class hierarchy of the three types of exceptions along with
some examples of errors, checked exceptions, and runtime exceptions. You can always
determine what category an exception fi ts into by whether it subclasses RuntimeException ,
Exception , or Error .

FIGURE 3.11 The three categories of exceptions.

java.lang.Throwable

java.lang.Exception java.lang.Error

java.lang.ClassNotFoundException java.lang.AssertionError

java.io.IOException java.lang.LinkageError

java.sql.SQLException java.lang.VirtualMachineError

java.lang.InterruptedException java.io.IOError

java.lang.RuntimeException

java.lang.ArithmeticException

java.lang.ClassCastException

java.lang.NullPointerException

You might wonder why there is such a distinct categorizing of exceptions. The categories
are important because the compiler enforces a rule known as the Handle or Declare Rule
that only applies to checked exceptions. The Handle or Declare Rule states that if any
statement might throw a checked exception, it must do one of the following:
Handle the exception by enclosing the statement in a try block that provides a
corresponding handler for the exception.
The method that contains the statement must declare the checked exception in the
throws clause of the method declaration.