Can We Rely On String.isEmpty For Checking Null Condition On A String In Java?

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 && !acct.isEmpty()) 

Note the use of && here, rather than your || in the previous code; also note how in your previous code, your conditions were wrong anyway - even with && you would only have entered the if body if acct was an empty string.

Alternatively, using Guava:

if (!Strings.isNullOrEmpty(acct)) 

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.

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())); }