Beginning Java 9 Fundamentals by Kishori Sharan

Author:Kishori Sharan
Language: eng
Format: epub
Publisher: Apress, Berkeley, CA

// May throw Exception2

}

} catch(Exception2 e2) {

// Handle Exception2 here

}

The following snippet of code shows how to catch an exception of one type and rethrow an exception of another type:

try {

// Code that might throw a MyException

} catch(MyException e) {

e.printStackTrace(); // Print the stack trace

// Rethrow a RuntimeException

throw new RuntimeException(e.getMessage());

}

The catch block catches the MyException, prints its stack trace, and rethrows a RuntimeException. In the process, it loses the details of the original exception that was thrown. When the RuntimeException is created, it packages the information of stack frames from the point where it was created. The client gets the information about the rethrown RuntimeException from the point it was created, not about the original MyException. In the previous code, you have hidden both the type and the location of the original exception from the client.

You can also rethrow another type of exception and use the original exception as the cause of the rethrown exception. It is as if the new exception is a wrapper for the original exception. You can set the cause of an exception using one of the constructors of the new exception type that accepts a cause as a parameter. You can also use the initCause() method to set the cause of the exception. The following snippet of code rethrows a RuntimeException setting MyException as its cause:

try {

// Code that might throw a MyException

} catch(MyException e) {

e.printStackTrace(); // Print the stack trace

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