[Chapter 6] 6.11 The throw Statement
Author: Mark Grand
Date: Thu Jul 31 13:14:43 1997

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| Chapter 6 Statements and Control Structures |

## 6.11 The throw Statement

A `throw` statement is used to cause an exception to be thrown:

The expression in a `throw` statement must produce a reference to an object that is an instance of the `Throwable` class or one of its subclasses. Otherwise, the compiler issues an error message. You typically want the expression in a `throw` statement to produce an object that is an instance of a subclass of the `Exception` class.

Here is an example of a `throw` statement:

    throw new ProtocolException();

A `throw` statement causes normal program execution to stop. Control is immediately transferred to the innermost enclosing `try` statement in the search for a `catch` clause that can handle the exception. If the innermost `try` statement cannot handle the exception, the exception propagates up through enclosing statements in the current method. If the current method does not contain a `try` statement that can handle the exception, the exception propagates up to the invoking method. If this method does not contain an appropriate `try` statement, the exception propagates up again, and so on. Finally, if no `try` statement is found to handle the exception, the currently running thread terminates. The termination of a thread is described in Stopping a thread.

As an exception propagates through enclosing `try` statements, any `finally` blocks associated with those `try` statements are executed until the exception is caught. If a `finally` block contains a `break`, `continue`, `return`, or `throw` statement, the pending control transfer initiated by the `throw` statement is forgotten. Instead, control is transferred to the target of the `break`, `continue`, `return`, or `throw` statement in the `finally` block.

References Exception Handling 9; Expression 4; The break Statement; The continue Statement; The return Statement; The try Statement; Throwable

The return Statement |  | The try Statement