How to check if String value is Boolean type in Java

Question

I did a little search on this but couldn t find anything useful   The point being that if String value is either  true  or  false  the return value should be true  In every other value it should be false   I tried these   String value    false   System out println  test1      Boolean parseBoolean value    System out println  test2      Boolean valueOf value    System out println  test3      Boolean getBoolean value      All functions returned false

User · Answer

Actually  checking for a Boolean type in a String  which is a type  is impossible  Basically you re asking how to do a  string compare   Like others stated  You need to define when you want to return  quot true quot  or  quot false quot   under what conditions   Do you want it to be case in sensitive  What if the value is null  I think Boolean valueOf   is your friend  javadoc says   Returns a Boolean with a value represented by the specified String  The Boolean returned represents the value true if the string argument is not null and is equal  ignoring case  to the string  quot true quot   Example  Boolean valueOf  quot True quot   returns true  Example  Boolean valueOf  quot yes quot   returns false

User · Answer

I suggest that you take a look at the Java docs for these methods  It appears that you are using them incorrectly  These methods will not tell you if the string is a valid boolean value  but instead they return a boolean  set to true or false  based on the string that you pass in   true  or  false    http   www j2ee me javase 6 docs api java lang Boolean html

User · Answer

parseBoolean String  returns true if the String is  case-insensitive   true   otherwise false valueOf String  ditto  returns the canonical Boolean Objects getBoolean String  is a red herring  it fetches the System property of the given name and compares that to  true    There exists no method to test whether a String encodes a Boolean  for all practical effects  any non- true -String is  false

User · Answer

Apache commons-lang3 has BooleanUtils with a method toBooleanObject   BooleanUtils toBooleanObject String str      where    BooleanUtils toBooleanObject null       null BooleanUtils toBooleanObject  true      Boolean TRUE BooleanUtils toBooleanObject  false     Boolean FALSE BooleanUtils toBooleanObject  on        Boolean TRUE BooleanUtils toBooleanObject  ON        Boolean TRUE BooleanUtils toBooleanObject  off       Boolean FALSE BooleanUtils toBooleanObject  oFf       Boolean FALSE BooleanUtils toBooleanObject  blue      null

User · Answer

return  true  equals value      false  equals value

User · Answer

function isBooleanString val        if  val      true     val      false          return true       else         return false           isBooleanString  true      true isBooleanString  false      true  isBooleanString  blabla      false

User · Answer

Yes  but  didn t you parse  false   If you parse  true   then they return true   Maybe there s a misunderstanding  the methods don t test  if the String content represents a boolean value  they evaluate the String content to boolean

User · Answer

Something you should also take into consideration is character casing     Instead of   return value equals  false      value equals  true      Do this   return value equalsIgnoreCase  false      value equalsIgnoreCase  true

User · Answer

The methods you re calling on the Boolean class don t check whether the string contains a valid boolean value  but they return the boolean value that represents the contents of the string  put  true  in string  they return true  put  false  in string  they return false   You can surely use these methods  however  to check for valid boolean values  as I d expect them to throw an exception if the string contains  hello  or something not boolean   Wrap that in a Method ContainsBoolString and you re go   EDIT By the way  in C  there are methods like bool Int32 TryParse string x  out int i  that perform the check whether the content can be parsed and then return the parsed result    int i  if  Int32 TryParse  Hello   out i        Hello is an int and its value is in i else      Hello is not an int   Benchmarks indicate they are way faster than the following   int i  try      i   Int32 Parse  Hello          Hello is an int and its value is in i   catch         Hello is not an int     Maybe there are similar methods in Java  It s been a while since I ve used Java

User · Answer

Can also do it by regex   Pattern queryLangPattern   Pattern compile  true false   Pattern CASE INSENSITIVE   Matcher matcher   queryLangPattern matcher booleanParam   return matcher matches

User · Answer

Here s a method you can use to check if a value is a boolean   boolean isBoolean String value        return value    null  amp  amp  Arrays stream new String    true    false    1    0                 anyMatch b - gt  b equalsIgnoreCase value        Examples of using it   System out println isBoolean null      false System out println isBoolean         false System out println isBoolean  true       true System out println isBoolean  fALsE       true System out println isBoolean  asdf       false System out println isBoolean  01truefalse       false

User · Answer

String value    True   boolean result   value equalsIgnoreCase  true     true   false

User · Answer

return value equals  false      value equals  true

User · Answer

if   true  equals value      false  equals value          do something   else        do something else

User · Answer

See oracle docs  public static boolean parseBoolean String s            return   s    null   amp  amp  s equalsIgnoreCase  true

User · Answer

Well for this  also have a look at org apache commons lang BooleanUtils toBoolean java lang String   along with many other useful functions

[java] How to check if String value is Boolean type in Java?

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