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    Sub-task 
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    Resolution: Unresolved
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     P5 P5
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    None
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    None
                    Make sure any exceptions thrown at creation time are explicit about what's wrong.
* ensure that exceptions for duplicate set elements and map keys report the duplicate value
http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-November/036854.html (Paul Benedict)
* report which argument is null
http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-November/036948.html (Roger Riggs)
            
* ensure that exceptions for duplicate set elements and map keys report the duplicate value
http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-November/036854.html (Paul Benedict)
* report which argument is null
http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-November/036948.html (Roger Riggs)