Exceptions

Try ... catch ... finally

try {...}
catch (MyException e) {...}
catch (AnotherException e) {...}
finally {...}

• Catch blocks in the same function in which the exception was thrown will not be executed.
• Finally blocks are useful for cleanup code that must always be executed.
• Finally blocks always execute after the flow-of-control leaves the try block, whether by continue, break, return, throw, or finishing the try block.

Throw

• Any object that implements the Throwable interface can be thrown; however, generally only throw objects derived from class Exception.

if (x != 4)
    throw new MyException();

Throws

double MyMethod()
    throws ExceptionName [, ExceptionName]*
{...}

• Declares the exceptions that a method may throw.
• If a method might throw an exception, or doesn't handle one it might receive, the method must declare the exception.

Common exceptions

• ArithmeticException
• ArrayIndexOutOfBoundsException
• ClassCastException
• InterruptedException
• IOException
• NullPointerException
• OutOfMemoryException

Debugging

e.getMessage();       // Returns a descriptive string.
e.toString();         // Displays the exception type.
e.printStackTrace();  // Shows where the exception occurred.