Best way to verify string is empty or null

Question

i am sure this must have been asked before in different ways - as isEmptyOrNull is so common yet people implement it differently  but i have below curious query in terms of best available approach which is good for memory and performance both    1  Below does not account for all spaces like in case of empty XML tag  return inputString  null    inputString length    0    2  Below one takes care but trim can eat some performance   memory   return inputString  null    inputString trim   length    0    3  Combining one and two can save some performance   memory   As Chris suggested in comments   return inputString  null    inputString trim   length    0    inputString trim   length    0    4  Converted to pattern matcher  invoked only when string is non zero length   private static final Pattern p   Pattern compile    s      return inputString  null    inputString length    0    p matcher inputString  matches      5  Using libraries like -       Apache Commons  StringUtils isBlank isEmpty        or Spring  StringUtils isEmpty         or Guava  Strings isNullOrEmpty         or any other option

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springframework library Check whether the given String is empty    f StringUtils isEmpty str                String is blank or null

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Optional ofNullable label   map String  trim   map string - gt   label isEmpty   orElse false    OR  TextUtils isNotBlank label    the last solution will check if not null and trimm the str at the same time

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Useful method from Apache Commons    org apache commons lang StringUtils isBlank String str    https   commons apache org proper commons-lang javadocs api-2 6 org apache commons lang StringUtils html isBlank java lang String

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Just to show java 8 s stance to remove null values   String s   Optional ofNullable myString  orElse      if  s trim   isEmpty                  Makes sense if you can use Optional lt String gt

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Simply and clearly  if  str    null    str trim   length      0           str is empty

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If you have to test more than one string in the same validation  you can do something like this   import java util Optional  import java util function Predicate  import java util stream Stream   public class StringHelper      public static Boolean hasBlank String     strings         Predicate lt String gt  isBlank   s - gt  s    null    s trim   isEmpty         return Optional        ofNullable strings         map Stream  of         map stream - gt  stream anyMatch isBlank          orElse false            So  you can use this like StringHelper hasBlank  Hello   null            or  StringHelper hasBlank  Hello   in a generic form

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Haven t seen any fully-native solutions  so here s one   return str    null    str chars   allMatch Character  isWhitespace     Basically  use the native Character isWhitespace   function  From there  you can achieve different levels of optimization  depending on how much it matters  I can assure you that in 99 99999  of use cases  no further optimization is necessary    return str    null    str length      0    str chars   allMatch Character  isWhitespace     Or  to be really optimal  but hecka ugly    int len  if  str    null     len   str length       0  return true  for  int i   0  i  lt  len  i        if   Character isWhitespace str charAt i    return false    return true    One thing I like to do   Optional lt String gt  notBlank String s      return s    null    s chars   allMatch Character  isWhitepace         Optional empty         Optional of s           notBlank myStr  orElse  some default

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This one from Google Guava could check out  null and empty String  in the same time   Strings isNullOrEmpty  Your string       Add a dependency with Maven   lt dependency gt     lt groupId gt com google guava lt  groupId gt     lt artifactId gt guava lt  artifactId gt     lt version gt 20 0 lt  version gt   lt  dependency gt    with Gradle  dependencies     compile  com google guava guava 20 0

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To detect if a string is null or empty  you can use the following without including any external dependencies on your project and still keeping your code simple clean       if myString  null    myString isEmpty           do something     or if blank spaces need to be detected as well   if myString  null    myString trim   isEmpty           do something     you could easily wrap these into utility methods to be more concise since these are very common checks to make   public final class StringUtils       private StringUtils               public static bool isNullOrEmpty string s           if s  null    s isEmpty                 return true                    return false             public static bool isNullOrWhiteSpace string s           if s  null    s trim   isEmpty                 return true                    return false            and then call these methods via   if StringUtils isNullOrEmpty myString         and  if StringUtils isNullOrWhiteSpace myString

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In most of the cases  StringUtils isBlank str  from apache commons library would solve it  But if there is case  where input string being checked has null value within quotes  it fails to check such cases   Take an example where I have an input object which was converted into string using String valueOf obj  API  In case obj reference is null  String valueOf returns  null  instead of null   When you attempt to use  StringUtils isBlank  null    API fails miserably  you may have to check for such use cases as well to make sure your validation is proper

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With the openJDK 11 you can use the internal validation to check if the String is null or just white spaces  import jdk internal joptsimple internal Strings       String targetString  if  Strings isNullOrEmpty tragetString

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Apache Commons Lang has StringUtils isEmpty String str  method which returns true if argument is empty or null

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You can make use of Optional and Apache commons Stringutils library  Optional ofNullable StringUtils noEmpty string1   orElse string2     here it will check if the string1 is not null and not empty else it will return string2

[java] Best way to verify string is empty or null

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