How to check a string against null in java

Question

How can I check a string against null in java  I am using  stringname equalsignorecase null    but it s not working

User · Answer

With Java 7 you can use  if  Objects equals foo  null                 which will return true if both parameters are null

User · Answer

If we look at the implementation of the equalsIgnoreCase method  we find this part   if  string    null    count    string count        return false      So it will always return false if the argument is null  And this is obviously right  because the only case where it should return true is when equalsIgnoreCase was invoked on a null String  but  String nullString   null  nullString equalsIgnoreCase null     will definitely result in a NullPointerException   So equals methods are not designed to test whether an object is null  just because you can t invoke them on null

User · Answer

If the value returned is null  use    if value isEmpty       Sometime to check null  if value    null  in java  it might not give true even the String is null

User · Answer

Of course user351809  stringname equalsignorecase null  will throw NullPointerException  See  you have a string object stringname  which follows 2 possible conditions -     stringname has a some non-null string value  say  computer    Your code will work fine as it takes the form  computer  equalsignorecase null  and you get the expected response as false  stringname has a null value  Here your code will get stuck  as null equalsignorecase null  However  seems good at first look and you may hope response as true  but  null is not an object that can execute the equalsignorecase   method    Hence  you get the exception due to case 2  What I suggest you is to simply use stringname    null

User · Answer

This looks a bit strange  but     stringName    null       equals stringName    Never had any issues doing it this way  plus it s a safer way to check while avoiding potential null point exceptions

User · Answer

Sure it works  You re missing out a vital part of the code  You just need to do like this   boolean isNull   false  try       stringname equalsIgnoreCase null     catch  NullPointerException npe        isNull   true

User · Answer

Well  the last time someone asked this silly question  the answer was   someString equals  null     This  fix  only hides the bigger problem of how null becomes  null  in the first place  though

User · Answer

You can check with String    null  This works for me      String foo   null      if foo    null           System out println  String is null

User · Answer

Use TextUtils Method if u working in Android   TextUtils isEmpty str    Returns true if the string is null or 0-length  Parameters  str the string to be examined Returns  true if str is null or zero length    if TextUtils isEmpty str                str is null or lenght is 0         Below is source code of this method You can use direclty                Returns true if the string is null or 0-length          param str the string to be examined         return true if str is null or zero length             public static boolean isEmpty CharSequence str            if  str    null    str length      0              return true          else             return false

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Simple method   public static boolean isBlank String value        return  value    null    value equals        value equals  null      value trim   equals

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I realize this was answered a long time ago  but I haven t seen this posted  so I thought I d share what I do  This isn t particularly good for code readability  but if you re having to do a series of null checks  I like to use   String someString   someObject getProperty      null        someObject getProperty   trim      In this example  trim is called on the string  which would throw an NPE if the string was null or spaces  but on the same line  you can check for null or blank so you don t end up with a ton of  more  difficult to format if blocks

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There are two ways to do it  Say String  null or string equals      public class IfElse        public int ifElseTesting String a             return null          return  a   null   0  a length              public class ShortCutifElseTesting        public static void main String   args             Scanner scanner new Scanner System in           System out println  enter the string please             String a scanner nextLine                       if  a equals null                System out println  you are not correct                      else if a equals  bangladesh                 System out println  you are right                      else             System out println  succesful tested                        IfElse ie new IfElse            int result ie ifElseTesting a           System out println result               Check this example  Here is an another example of shortcut version of If Else

User · Answer

string    null compares if the object is null   string equals  foo   compares the value inside of that object   string     foo  doesn t always work  because you re trying to see if the objects are the same  not the values they represent    Longer answer   If you try this  it won t work  as you ve found   String foo   null  if  foo equals null            That fails every time       The reason is that foo is null  so it doesn t know what  equals is  there s no object there for  equals to be called from   What you probably wanted was   String foo   null  if  foo    null           That will work      The typical way to guard yourself against a null when dealing with Strings is   String foo   null  String bar    Some string       if  foo    null  amp  amp  foo equals bar            Do something here      That way  if foo was null  it doesn t evaluate the second half of the conditional  and things are all right   The easy way  if you re using a String literal  instead of a variable   is   String foo   null      if   some String  equals foo            Do something here      If you want to work around that  Apache Commons has a class - StringUtils - that provides null-safe String operations     if  StringUtils equals foo  bar            Do something here      Another response was joking  and said you should do this    boolean isNull   false  try       stringname equalsIgnoreCase null     catch  NullPointerException npe        isNull   true      Please don t do that   You should only throw exceptions for errors that are exceptional  if you re expecting a null  you should check for it ahead of time  and not let it throw the exception     In my head  there are two reasons for this   First  exceptions are slow  checking against null is fast  but when the JVM throws an exception  it takes a lot of time   Second  the code is much easier to read and maintain if you just check for the null pointer ahead of time

User · Answer

I m not sure what was wrong with The MYYN s answer     if  yourString    null        do fun stuff with yourString here     The above null check is quite alright     If you are trying to check if a String reference is equal  ignoring case  to another string that you know is not a null reference  then do something like this   String x    this is not a null reference  if  x equalsIgnoreCase yourStringReferenceThatMightBeNull          do fun stuff     If there is any doubt as to whether or not you have null references for both Strings you are comparing  you ll need to check for a null reference on at least one of them to avoid the possibility of a NullPointerException

User · Answer

If your string having  null  value then you can use  if null    stringName       code      else   Error Msg

User · Answer

import it in your class   import org apache commons lang StringUtils    then use it  they both will return true  System out println StringUtils isEmpty       System out println StringUtils isEmpty null

User · Answer

s    null   won t work

User · Answer

If I understand correctly  this should do it  if  stringname isEmpty       an if to check if stringname is not null if stringname isEmpty       an if to check if stringname is null

[java] How to check a string against null in java?

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