What does a Cannot find symbol or Cannot resolve symbol error mean

Question

Please explain the following about  quot Cannot find symbol quot    quot Cannot resolve symbol quot  or  quot Symbol not found quot  errors   What do they mean  What things can cause them  How does the programmer go about fixing them   This question is designed to seed a comprehensive Q amp A about these common compilation errors in Java

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If you re getting this error in the build somewhere else  while your IDE says everything is perfectly fine  then check that you are using the same Java versions in both places   For example  Java 7 and Java 8 have different APIs  so calling a non-existent API in an older Java version would cause this error

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SOLVED Using IntelliJ Select Build- gt Rebuild Project will solve it

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We got the error in a Java project that is set up as a Gradle multi-project build  It turned out that one of the sub-projects was missing the Gradle Java Library plugin  This prevented the sub-project s class files from being visible to other projects in the build  After adding the Java library plugin to the sub-project s build gradle in the following way  the error went away  plugins               id  java-library

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You ll also get this error if you forget a new   String s   String      versus  String s   new String      because the call without the new keyword will try and look for a  local  method called String without arguments - and that method signature is likely not defined

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you compiled your code using maven compile and then used maven test to run it worked fine  Now if you changed something in your code and then without compiling you are running it  you will get this error   Solution  Again compile it and then run test  For me it worked this way

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One more example of  Variable is out of scope   As I ve seen that kind of questions a few times already  maybe one more example to what s illegal even if it might feel okay   Consider this code   if somethingIsTrue        String message    Everything is fine     else     String message    We have an error     System out println message     That s invalid code  Because neither of the variables named message is visible outside of their respective scope - which would be the surrounding brackets    in this case    You might say   But a variable named message is defined either way - so message is defined after the if     But you d be wrong    Java has no free   or delete operators  so it has to rely on tracking variable scope to find out when variables are no longer used  together with references to these variables of cause     It s especially bad if you thought you did something good  I ve seen this kind of error after  optimizing  code like this   if somethingIsTrue        String message    Everything is fine     System out println message     else     String message    We have an error     System out println message        Oh  there s duplicated code  let s pull that common line out  -  and there it it   The  most common way to deal with this kind of scope-trouble would be to pre-assign the else-values to the variable names in the outside scope and then reassign in if   String message    We have an error   if somethingIsTrue        message    Everything is fine      System out println message

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In my case - I had to perform below operations    Move context xml file from src java package to the resource directory  IntelliJ IDE  Clean target directory

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Can not find   means that   compiler who can t find appropriate variable  method  class etc   if you got that error massage   first of all you want to find code line where get error massage  And then you will able to find which variable   method or class have not define before using it After confirmation  initialize that variable  method or class can be used for later require   Consider the following example   I ll create a demo class and print a name     class demo         public static void main String a                  System out print name               Now look at the result      That error says   variable name can not find   Defining and initializing value for  name  variable  can be abolished that error  Actually like this   class demo         public static void main String a                   String name  smith                 System out print name               Now look at the new output       Ok Successfully solved that error  At the same time   if you could get  can not find method   or  can not find class  something   At first define a class or method and after use that

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If eclipse Java build path is mapped to 7  8 and in Project pom xml Maven properties java version is mentioned higher Java version 9 10 11  etc     than 7 8 you need to update in pom xml file   In Eclipse if Java is mapped to Java version 11 and in pom xml it is mapped to Java version 8  Update Eclipse support to Java 11 by go through below steps in eclipse IDE Help -  Install New Software -    Paste following link http   download eclipse org eclipse updates 4 9-P-builds at Work With  or  Add  Popup window will open  -   Name  Java 11 support Location  http   download eclipse org eclipse updates 4 9-P-builds  then update Java version in Maven properties of pom xml file as below   lt java version gt 11 lt  java version gt   lt maven compiler source gt   java version  lt  maven compiler source gt   lt maven compiler target gt   java version  lt  maven compiler target gt    Finally do right click on project Debug as -  Maven clean  Maven build steps

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0  Is there any difference between the two errors  Not really   quot Cannot find symbol quot    quot Cannot resolve symbol quot  and  quot Symbol not found quot  all mean the same thing   Different Java compilers use different phraseology  1  What does a  Cannot find symbol  error mean  Firstly  it is a compilation error1   It means that either there is a problem in your Java source code  or there is a problem in the way that you are compiling it  Your Java source code consists of the following things   Keywords  like true  false  class  while  and so on  Literals  like 42 and  X  and  quot Hi mum  quot   Operators and other non-alphanumeric tokens  like          and so on  Identifiers  like Reader  i  toString  processEquibalancedElephants  and so on  Comments and whitespace   A  quot Cannot find symbol quot  error is about the identifiers   When your code is compiled  the compiler needs to work out what each and every identifier in your code means  A  quot Cannot find symbol quot  error means that the compiler cannot do this   Your code appears to be referring to something that the compiler doesn t understand  2  What can cause a  Cannot find symbol  error  As a first order  there is only one cause   The compiler looked in all of the places where the identifier should be defined  and it couldn t find the definition   This could be caused by a number of things   The common ones are as follows   For identifiers in general   Perhaps you spelled the name incorrectly  i e  StringBiulder instead of StringBuilder   Java cannot and will not attempt to compensate for bad spelling or typing errors  Perhaps you got the case wrong  i e  stringBuilder instead of StringBuilder   All Java identifiers are case sensitive  Perhaps you used underscores inappropriately  i e  mystring and my string are different    If you stick to the Java style rules  you will be largely protected from this mistake      Perhaps you are trying to use something that was declared  quot somewhere else quot   i e  in a different context to where you have implicitly told the compiler to look    A different class   A different scope   A different package   A different code-base     For identifiers that should refer to variables   Perhaps you forgot to declare the variable  Perhaps the variable declaration is out of scope at the point you tried to use it    See example below    For identifiers that should be method or field names   Perhaps you are trying to refer to an inherited method or field that wasn t declared in the parent   ancestor classes or interfaces   Perhaps you are trying to refer to a method or field that does not exist  i e  has not been declared  in the type you are using  e g   quot someString quot  push  2   Perhaps you are trying to use a method as a field  or vice versa  e g   quot someString quot  length or someArray length     Perhaps you are mistakenly operating on an array rather than array element  e g      String strings             if  strings charAt 3                  maybe that should be  strings 0  charAt 3       For identifiers that should be class names   Perhaps you forgot to import the class   Perhaps you used  quot star quot  imports  but the class isn t defined in any of the packages that you imported   Perhaps you forgot a new as in      String s   String        should be  new String        For cases where type or instance doesn t appear to have the member you were expecting it to have   Perhaps you have declared a nested class or a generic parameter that shadows the type you were meaning to use  Perhaps you are shadowing a static or instance variable  Perhaps you imported the wrong type  e g  due to IDE completion or auto-correction  Perhaps you are using  compiling against  the wrong version of an API  Perhaps you forgot to cast your object to an appropriate subclass     The problem is often a combination of the above   For example  maybe you  quot star quot  imported java io   and then tried to use the Files class     which is in java nio not java io   Or maybe you meant to write File     which is a class in java io   Here is an example of how incorrect variable scoping can lead to a  quot Cannot find symbol quot  error  List lt String gt  strings        for  int i   0  i  lt  strings size    i          if  strings get i  equalsIgnoreCase  quot fnord quot              break          if  i  lt  strings size                 This will give a  quot Cannot find symbol quot  error for i in the if statement   Though we previously declared i  that declaration is only in scope for the for statement and its body   The reference to i in the if statement cannot see that declaration of i   It is out of scope   An appropriate correction here might be to move the if statement inside the loop  or to declare i before the start of the loop    Here is an example that causes puzzlement where a typo leads to a seemingly inexplicable  quot Cannot find symbol quot  error  for  int i   0  i  lt  100  i           System out println  quot i is  quot    i      This will give you a compilation error in the println call saying that i cannot be found   But  I hear you say  I did declare it  The problem is the sneaky semicolon       before the     The Java language syntax defines a semicolon in that context to be an empty statement   The empty statement then becomes the body of the for loop   So that code actually means this  for  int i   0  i  lt  100  i          The previous and following are separate statements          System out println  quot i is  quot    i      The         block is NOT the body of the for loop  and therefore the previous declaration of i in the for statement is out of scope in the block   Here is another example of  quot Cannot find symbol quot  error that is caused by a typo  int tmp       int res   tmp a   b    Despite the previous declaration  the tmp in the tmp      expression is erroneous   The compiler will look for a method called tmp  and won t find one   The previously declared tmp is in the namespace for variables  not the namespace for methods  In the example I came across  the programmer had actually left out an operator   What he meant to write was this  int res   tmp    a   b     There is another reason why the compiler might not find a symbol if you are compiling from the command line   You might simply have forgotten to compile or recompile some other class   For example  if you have classes Foo and Bar where Foo uses Bar   If you have never compiled Bar and you run javac Foo java  you are liable to find that the compiler can t find the symbol Bar   The simple answer is to compile Foo and Bar together  e g  javac Foo java Bar java or javac   java   Or better still use a Java build tool  e g  Ant  Maven  Gradle and so on  There are some other more obscure causes too     which I will deal with below  3  How do I fix these errors   Generally speaking  you start out by figuring out what caused the compilation error   Look at the line in the file indicated by the compilation error message  Identify which symbol that the error message is talking about  Figure out why the compiler is saying that it cannot find the symbol  see above   Then you think about what your code is supposed to be saying   Then finally you work out what correction you need to make to your source code to do what you want  Note that not every  quot correction quot  is correct  Consider this  for  int i   1  i  lt  10  i          for  j   1  j  lt  10  j                           Suppose that the compiler says  quot Cannot find symbol quot  for j   There are many ways I could  quot fix quot  that   I could change the inner for to for  int j   1  j  lt  10  j    - probably correct  I could add a declaration for j before the inner for loop  or the outer for loop - possibly correct  I could change j to i in the inner for loop - probably wrong  and so on   The point is that you need to understand what your code is trying to do in order to find the right fix  4   Obscure causes Here are a couple of cases where the  quot Cannot find symbol quot  is seemingly inexplicable     until you look closer   Incorrect dependencies  If you are using an IDE or a build tool that manages the build path and project dependencies  you may have made a mistake with the dependencies  e g  left out a dependency  or selected the wrong version   If you are using a build tool  Ant  Maven  Gradle  etc   check the project s build file   If you are using an IDE  check the project s build path configuration   You are not recompiling   It sometimes happens that new Java programmers don t understand how the Java tool chain works  or haven t implemented a repeatable  quot build process quot   e g  using an IDE  Ant  Maven  Gradle and so on   In such a situation  the programmer can end up chasing his tail looking for an illusory error that is actually caused by not recompiling the code properly  and the like      An earlier build problem   It is possible that an earlier build failed in a way that gave a JAR file with missing classes   Such a failure would typically be noticed if you were using a build tool   However if you are getting JAR files from someone else  you are dependent on them building properly  and noticing errors   If you suspect this  use tar -tvf to list the contents of the suspect JAR file   IDE issues  People have reported cases where their IDE gets confused and the compiler in the IDE cannot find a class that exists     or the reverse situation   This could happen if the IDE has been configured with the wrong JDK version   This could happen if the IDE s caches get out of sync with the file system   There are IDE specific ways to fix that   This could be an IDE bug   For instance  Joel Costigliola describes a scenario where Eclipse does not handle a Maven  quot test quot  tree correctly  see this answer     Android issues  When you are programming for Android  and you have  quot Cannot find symbol quot  errors related to R  be aware that the R symbols are defined by the context xml file   Check that your context xml file is correct and in the correct place  and that the corresponding R class file has been generated   compiled   Note that the Java symbols are case sensitive  so the corresponding XML ids are be case sensitive too  Other symbol errors on Android are likely to be due to previously mention reasons  e g  missing or incorrect dependencies  incorrect package names  method or fields that don t exist in a particular API version  spelling   typing errors  and so on   Redefining system classes  I ve seen cases where the compiler complains that substring is an unknown symbol in something like the following String s       String s1   s substring 1    It turned out that the programmer had created their own version of String and that his version of the class didn t define a substring methods  Lesson  Don t define your own classes with the same names as common library classes   Homoglyphs   If you use UTF-8 encoding for your source files  it is possible to have identifiers that look the same  but are in fact different because they contain homoglyphs    See this page for more information  You can avoid this by restricting yourself to ASCII or Latin-1 as the source file encoding  and using Java  uxxxx escapes for other characters     1 - If  perchance  you do see this in a runtime exception or error message  then either you have configured your IDE to run code with compilation errors  or your application is generating and compiling code    at runtime  2 - The three basic principles of Civil Engineering  water doesn t flow uphill  a plank is stronger on its side  and you can t push on a string

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I solved this error like this    The craziness of android  I had the package name as Adapter and the I refactor the name to adapter with an  quot a quot  instead of  quot A quot  and solved the error

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There can be various scenarios as people have mentioned above  A couple of things which have helped me resolve this    If you are using IntelliJ  File - gt   Invalidate Caches Restart    OR   The class being referenced was in another project and that dependency was not added to the Gradle build file of my project  So I added the dependency using  compile project   anotherProject     and it worked  HTH

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For hints  look closer at the class name name that throws an error and the line number  example  Compilation failure  ERROR   applications xxxxx java  44 30  error  cannot find symbol  One other cause is unsupported method of for java version say jdk7 vs 8  Check your  JAVA HOME

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I too was getting this error   for which I googled and I was directed to this page   Problem  I was calling a static method defined in the class of a project A from a class defined in another project B   I was getting the following error   error  cannot find symbol   Solution  I resolved this by first building the project where the method is defined then the project where the method was being called from

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One way to get this error in Eclipse      Define a class A in src test java  Define another class B in src main java that uses class A    Result   Eclipse will compile the code  but maven will give  Cannot find symbol    Underlying cause   Eclipse is using a combined build path for the main and test trees   Unfortunately  it does not support using different build paths for different parts of an Eclipse project  which is what Maven requires   Solution      Don t define your dependencies that way  i e  don t make this mistake  Regularly build your codebase using Maven so that you pick up this mistake early   One way to do that is to use a CI server

[java] What does a "Cannot find symbol" or "Cannot resolve symbol" error mean?

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