Can we rely on String isEmpty for checking null condition on a String in Java

Question

I am passing an accountid as input from an XML file as shown  which will be parsed later  and will be  used in our code    lt accountid gt 123456 lt  accountid gt   lt user gt pavan lt  user gt    The issue is that if nothing is passed  null value in accoutnid  is passed as accountid  I could not able to handle that situation in Java code  I tried this but I was not successful   if  acct    null  acct      acct equals                the above is not working      I was able to handle this successfully using the following approach   if  acct isEmpty            thisis working      Can we rely on the String isEmpty   method for checking the null condition of a String  Is this valid

User · Accepted Answer

No  absolutely not - because if acct is null  it won t even get to isEmpty    it will immediately throw a NullPointerException   Your test should be   if  acct    null  amp  amp   acct isEmpty      Note the use of  amp  amp  here  rather than your    in the previous code  also note how in your previous code  your conditions were wrong anyway - even with  amp  amp  you would only have entered the if body if acct was an empty string   Alternatively  using Guava   if   Strings isNullOrEmpty acct

User · Answer

Use StringUtils isEmpty instead  it will also check for null   Examples are    StringUtils isEmpty null         true  StringUtils isEmpty              true  StringUtils isEmpty              false  StringUtils isEmpty  bob         false  StringUtils isEmpty    bob       false   See more on official Documentation on String Utils

User · Answer

You can t use String isEmpty   if it is null  Best is to have your own method to check null or empty    public static boolean isBlankOrNull String str        return  str    null       equals str trim

User · Answer

I think the even shorter answer that you ll like is  StringUtils isBlank acct   From the documentation  http   commons apache org proper commons-lang javadocs api-2 6 org apache commons lang StringUtils html isBlank 28java lang String 29 isBlank public static boolean isBlank String str  Checks if a String is whitespace  empty   quot  quot   or null    StringUtils isBlank null         true  StringUtils isBlank  quot  quot            true  StringUtils isBlank  quot   quot           true  StringUtils isBlank  quot bob quot         false  StringUtils isBlank  quot   bob   quot     false   Parameters  str - the String to check  may be null Returns  true if the String is null  empty or whitespace

User · Answer

String s1        empty string assigned to s1   s1 has length 0  it holds a value of no length string  String s2 null     absolutely nothing  it holds no value  you are not assigning any value to s2   so null is not the same as empty   hope that helps

User · Answer

No  the String isEmpty   method looks as following   public boolean isEmpty         return this value length    0      as you can see it checks the length of the string so you definitely have to check if the string is null before

[java] Can we rely on String.isEmpty for checking null condition on a String in Java?

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