Java Checked vs Unchecked Exception

Some guidelines about check and uncheck exception:

• Only exceptions that will cause a method to complete abruptly should appear in its throws clause.

• There are two kinds of exceptions in Java, checked and unchecked, and only checked exceptions need appear in throws clauses.

• Any checked exceptions that may be thrown in a method must either be caught or declared in the method's throws clause.

• Whether or not an exception is "checked" is determined by its position in the hierarchy of throwable classes.

• To create a new checked exception, you simply extend another checked exception. All throwables that are subclasses of Exception, but not subclasses of RuntimeException are checked exceptions.

• Most unchecked throwables declared in java.lang (subclasses of Error and RuntimeException) are problems that would be detected by the Java virtual machine.

• Errors usually signal abnormal conditions that you wouldn't want a program to handle.

• If you are throwing an exception to indicate an improper use of your class, you are signalling a software bug. The class of exception you throw probably should descend from RuntimeException, which will make it unchecked. Otherwise, if you are throwing an exception to indicate not a software bug but an abnormal condition that client programmers should deal with every time they use your method, your exception should be checked.

• At least one clause, either catch or finally, must be associated with each try block. If you have both catch clauses and a finally clause with the same try block, you must put the finally clause after all the catch clauses