A throw statement may throw any expression that may be assigned to the Throwable type.
In Java, the throw
statement is used to explicitly throw an exception. When you use the throw
statement, you typically throw an instance of a class that extends either Throwable
, which is the base class for all exceptions and errors, or one of its subclasses.
The two main subclasses of Throwable
are:
- Exception: This is the class most commonly used for exceptional conditions that a program should catch. It further has two subclasses:
- Checked exceptions: These are exceptions that must be either caught or declared to be thrown in the method in which they occur. Examples include
IOException
andSQLException
. - Unchecked exceptions (Runtime exceptions): These are exceptions that do not need to be explicitly caught or declared. They usually indicate programming bugs or errors. Examples include
NullPointerException
,ArrayIndexOutOfBoundsException
, andArithmeticException
.
- Checked exceptions: These are exceptions that must be either caught or declared to be thrown in the method in which they occur. Examples include
- Error: This class is used for exceptional conditions that should not be caught by ordinary application code. Errors are typically reserved for situations where recovery is not possible. Examples include
OutOfMemoryError
andStackOverflowError
.
So, when you use the throw
statement, you can throw instances of classes that extend either Exception
or Error
, and their subclasses.