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How can i effectively use without causing NPE?  RSS feed

 
Greenhorn
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Existing code:

if (messsage !="" && messsage !=null && (err=="" || err==null)){

NewCode:

if (messsage !="" && messsage !=null && (err.equals("") || err.equals(null))){

If i modify the code as above , will there be an issue? i am doing it to prevent security exceptions of '==' operator.


 
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What security exception are there with == operator?

You shouldn't use == to compare strings.

You coud use a 'reversed' notation to avoid NPE, like: if(!"".equals(message)). I'll let you decide if it looks readable enough.

Writing err.equals("") || err.equals(null) won't guard you against a NPE.
First, you should always check for null first. If err is null then err.equals("") will throw a NPE.
Second, err.equals(null) is an incorrect way to do a null check. It will throw NPE if err is null. Also, a properly designed equals method (String class has one) will never return true for null argument. For a null check you have to use the == operator.
 
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