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Null Boolean Values?

Posted on 2016-08-08
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Last Modified: 2016-08-09
intejiaIdea null defintionNull boolean values. Can someone simplify the explanation in the photo.

I understand that we can set Boolean values to false or true using mathematical calculations or string setting, but am confused as to when a Boolean would ever be "Null" or "NotNull".
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Question by:rgb192
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dpearson earned 500 total points
ID: 41748173
In Java "bool" and "Boolean" are not quite equivalent.

"bool" is a primitive and only has 2 possible values - "true" or "false.
"Boolean" is an object and there can have 3 possible values - Boolean.TRUE, Boolean.FALSE or null.

e.g.
Boolean x = null ; // Legal
bool x = null ;  // Won't compile

That being said, this warning is actually saying that they've looked at your code and figured out that "m1 is always 3".

So B5 = (m1 != 3) ; will always be false (since m1 is always 3).  The null/non-null stuff isn't really coming into play in this instance - although it is good to understand them.

Hope that helps,

Doug
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Expert Comment

by:HuaMinChen
ID: 41748193
A boolean can be defaulted to 'false'. In your case, it is true when m1 does not equal to 3.
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Author Closing Comment

by:rgb192
ID: 41749578
true false null
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