1) if(null != parentObj.childObj)
2) if(parentObj.childObj != null)
Do you think that "1" will avoid a potential null pointer exception in the case where 'parentObj' is null, in contrast to "2"?
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3 Answers
No.
If parentObj is null then any attempt to call a method or reference a field will result in a NullPointerExcepton. != always evaluates both sides.
Just check if parentObj is null first and handle it appropriately.
Comments
Why not just if(parentObj != null && parentObj.childObj != null) ?
2 Comments
Tony Ennis
That's what the OP is asking. He's looking to avoid the wordiness of the check.
Stephen C
@Tony Ennis. 1) That's not how I read the question. 2) Anyway, the answer is that he can't, and @irrelephant's answer provides him with the sanest alternative.
If parentObj is null, referencing any method/field on parentObj will result in an NPE. In other words, you need if (parentObj != null && parentObj.childObj != null) to avoid an NPE. Groovy cuts down on this (very common) type of verbosity with the safe navigation operator, which lets you write if (parentObj?.childObj).
1 Comment
Stephen C
At one point, the safe navigation operator or something similar might have made it into Java 7 via project Coin. But it didn't make the cut; see blogs.sun.com/darcy/entry/project_coin_final_five
