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    <p>Have you considered using a RuntimeException (unchecked) wrapper class to smuggle the original exception out of the lambda expression, then casting the wrapped exception <em>back</em> to it's original checked exception?</p> <pre><code>class WrappedSqlException extends RuntimeException { static final long serialVersionUID = 20130808044800000L; public WrappedSqlException(SQLException cause) { super(cause); } public SQLException getSqlException() { return (SQLException) getCause(); } } public ConnectionPool(int maxConnections, String url) throws SQLException { try { super(() -&gt; { try { return DriverManager.getConnection(url); } catch ( SQLException ex ) { throw new WrappedSqlException(ex); } }, maxConnections); } catch (WrappedSqlException wse) { throw wse.getSqlException(); } } </code></pre> <p>Creating your own unique class should prevent any likelihood of mistaking another unchecked exception for the one you wrapped inside your lambda, even if the exception is serialized somewhere in the pipeline before you catch and re-throw it.</p> <p>Hmm... The only thing I see that's a problem here is that you are doing this inside a constructor with a call to super() which, by law, must be the first statement in your constructor. Does <code>try</code> count as a previous statement? I have this working (without the constructor) in my own code.</p>
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    1. POJava 8: Mandatory checked exceptions handling in lambda expressions. Why mandatory, not optional?
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    1. USGlenPeterson
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    1. COThank you for reply. I would really like to prevent explicit `try/catch`ing in lambda expressions because `try/catch` blocks look ugly making the lambdas ugly too. I guess there are at least two reasons of why it cannot work like that so far: 1) the history of Java itself; 2) a method, that's invoked with a lambda expression having methods with `throws` invocations inside, probably should be "automatically" declared as "`throws` _SomeEx_", even if the method is declared without any `throws` or it declares to throw exception of another type rather than could be propagated from the lambda.
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      1. USLyubomyr Shaydariv
    2. CO3) If it could "swallow" checked exceptions, I think, then it might break your expectations for a checked exception or unchecked exception you might expect to catch in any caller outside. For example, you could expect to catch `IOException` for currently illegal code like `list.forEach(p -> outputStream.write(p.hashCode()))` (`write()` throws `IOException`), but you'd probably couldn't do it, because `Iterable.forEach()` is not declared as a method throwing `IOException`, so a compiler cannot know of these intentions. Sometimes checked exceptions are really harmful...
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      1. USLyubomyr Shaydariv
    3. COI agree. It would be overkill to provide a second set of java.util.function classes that declare that they throw a (checked) Exception. Especially since we'd need two versions of every method with a function parameter - one that throws and one that doesn't. That goes a long way toward explaining why Scala doesn't have checked exceptions (only unchecked). Java 8 is a copy of Scala's lambdas with a `->` instead of `=>`. I wonder if Martin Odersky suggested any of this while he was working at Sun? I hope Java 9 includes immutable versions of most of their API classes.
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