EJ-61 Exception Chaining: Throw Exceptions Appropriate to the Abstraction

Ref: Effective Java by Joshua Bloch

It is disconcerting when a method throws an exception that has no appropriate connection to the task that it performs. Higher layers should catch lower-level exceptions and in their place, throw exceptions that can be explained in terms of the higher-level abstraction. This idiom is known as exception translation:

	// Exception Translation
	try {
	// Use lower-level abstraction to do our bidding
	...
	} catch(LowerLevelException e) {
	throw new HigherLevelException(...);
	}

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 A special form of exception translation called exception chaining is appropriate in cases where the lower-level exception might be helpful to someone debugging the problem that caused the higher-level exception.

	// Exception Chaining
	try {
	... // Use lower-level abstraction to do our bidding
	} catch (LowerLevelException cause) {
	throw new HigherLevelException(cause);
	}

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