Getting the class name from a static method in Java

Question

How can one get the name of the class from a static method in that class  For example  public class MyClass       public static String getClassName             String name            what goes here so the string  MyClass  is returned         return name            To put it in context  I actually want to return the class name as part of a message in an exception

User · Answer

So  we have a situation when we need to statically get class object or a class full simple name without an explicit usage of MyClass class syntax   It can be really handy in some cases  e g  logger instance for the kotlin upper-level functions  in this case kotlin creates a static Java class not accessible from the kotlin code    We have a few different variants for getting this info    new Object     getClass   getEnclosingClass    noted by Tom Hawtin - tackline getClassContext   0  getName    from the SecurityManager noted by Christoffer new Throwable   getStackTrace   0  getClassName    by count ludwig Thread currentThread   getStackTrace   1  getClassName    from Keksi and finally awesome MethodHandles lookup   lookupClass    from Rein    I ve prepared a jmh benchmark for all variants and results are     Run complete  Total time  00 04 18  Benchmark                                                      Mode  Cnt      Score     Error  Units StaticClassLookup MethodHandles lookup lookupClass             avgt   30      3 630      0 024  ns op StaticClassLookup AnonymousObject getClass enclosingClass      avgt   30    282 486      1 980  ns op StaticClassLookup SecurityManager classContext 1               avgt   30    680 385     21 665  ns op StaticClassLookup Thread currentThread stackTrace 1 className  avgt   30  11179 460    286 293  ns op StaticClassLookup Throwable stackTrace 0 className             avgt   30  10221 209    176 847  ns op     Conclusions   Best variant to use  rather clean and monstrously fast  Available only since Java 7 and Android API 26      MethodHandles lookup   lookupClass       In case you need this functionality for Android or Java 6  you can use the second best variant  It s rather fast too  but creates an anonymous class in each place of usage        new Object     getClass   getEnclosingClass       If you need it in many places and don t want your bytecode to bloat due to tons of anonymous classes     SecurityManager is your friend  third best option    But you can t just call getClassContext       it s protected in the SecurityManager class  You will need some helper class like this         Helper class  public final class CallerClassGetter extends SecurityManager        private static final CallerClassGetter INSTANCE   new CallerClassGetter        private CallerClassGetter           public static Class lt   gt  getCallerClass             return INSTANCE getClassContext   1                 Usage example   class FooBar        static final Logger LOGGER   LoggerFactory getLogger CallerClassGetter getCallerClass          You probably don t ever need to use last two variants based on the getStackTrace   from exception or the Thread currentThread    Very inefficient and can return only the class name as a String  not the Class lt   gt  instance      P S   If you want to create a logger instance for static kotlin utils  like me     you can use this helper   import org slf4j Logger import org slf4j LoggerFactory     Should be inlined to get an actual class instead of the one where this helper declared    Will work only since Java 7 and Android API 26   Suppress  NOTHING TO INLINE   inline fun loggerFactoryStatic    Logger       LoggerFactory getLogger MethodHandles lookup   lookupClass      Usage example   private val LOGGER   loggerFactoryStatic           Returns a pseudo-random  uniformly distributed value between the    given least value  inclusive  and bound  exclusive          param min the least value returned     param max the upper bound  exclusive         return the next value     throws IllegalArgumentException if least greater than or equal to bound     see java util concurrent ThreadLocalRandom nextDouble double  double      fun Random nextDouble min  Double    0  max  Double   1 0   Double       if  min  gt   max            if  min    max  return max         LOGGER warn  nextDouble  min  min  gt  max  max           return min           return nextDouble      max - min    min

User · Answer

This instruction works fine   Thread currentThread   getStackTrace   1  getClassName

User · Answer

Abuse the SecurityManager  System getSecurityManager   getClassContext   0  getName      Or  if not set  use an inner class that extends it  example below shamefully copied from Real s HowTo    public static class CurrentClassGetter extends SecurityManager       public String getClassName             return getClassContext   1  getName

User · Answer

In Java 7  you can do this in static method fields   MethodHandles lookup   lookupClass

User · Answer

I have used these two approach for both static and non static scenario   Main class     For non static approach public AndroidLogger Object classObject        mClassName   classObject getClass   getSimpleName         For static approach public AndroidLogger String className        mClassName   className      How to provide class name   non static way   private AndroidLogger mLogger   new AndroidLogger this     Static way   private static AndroidLogger mLogger   new AndroidLogger Myclass class getSimpleName

User · Answer

If you are using reflection  you can get the Method object and then   method getDeclaringClass   getName     To get the Method itself  you can probably use   Class lt   gt  c   Class forName  class name    Method  method   c getDeclaredMethod   method name   parameterTypes

User · Answer

I use this to init the Log4j Logger at the top of my classes  or annotate    PRO  Throwable is already loaded and you might save resources by not using the  IO heavy  SecurityManager   CON  Some question as to whether this will work for all JVMs       Log4j   Logger --- Get class name in static context by creating an anonymous Throwable and     getting the top of its stack-trace      NOTE you must use  getClassName   because getClass   just returns StackTraceElement class  static final Logger logger   Logger getLogger new Throwable    getStackTrace   0  getClassName

User · Answer

You could do something really sweet by using JNI like this   MyObject java   public class MyObject       static               System loadLibrary   classname                public static native String getClassName         public static void main  String   args                 System out println  getClassName                then   javac MyObject java javah -jni MyObject   then   MyObject c    include  MyObject h   JNIEXPORT jstring JNICALL Java MyObject getClassName  JNIEnv  env  jclass cls         jclass javaLangClass     env - gt FindClass  env   java lang Class         jmethodID getName     env - gt GetMethodID  env  javaLangClass   getName              Ljava lang String          return   env - gt CallObjectMethod  env  cls  getName        Then compile the C up into a shared library called libclassname so and run the java    chuckle

User · Answer

A refactoring-safe  cut amp paste-safe solution that avoids the definition of ad-hoc classes below   Write a static method that recover the class name having care to include the class name in the method name   private static String getMyClassName      return MyClass class getName        then recall it in your static method   public static void myMethod      Tracer debug getMyClassName     message        Refactoring safety is given by avoiding the use of strings  cut amp paste safety is granted because if you cut amp paste the caller method you won t find the getMyClassName   in the target  MyClass2  class  so you will be forced to redefine and update it

User · Answer

Do what  toolkit says  Do not do anything like this  return new Object       getClass   getEnclosingClass      Edit  Or if you are using a Java version that came out well after this answer was originally written   Rein

User · Answer

Verbatim use of caller s class like MyClass class getName   actually does the job  but is prone to copy paste errors if you propagate this code to numerous classes subclasses where you need this class name   And Tom Hawtin s recipe is in fact not bad  one just needs to cook it the right way     In case you have a base class with a static method that may be called from subclasses  and this static method needs to know the actual caller s class  this may be achieved like the following   class BaseClass     static sharedStaticMethod  String callerClassName  Object    otherArgs        useCallerClassNameAsYouWish  callerClassName          and direct use of  new Object       getClass   getEnclosingClass   getName           instead of  callerClassName  is not going to help here         as it returns  BaseClass         class SubClass1 extends BaseClass     static someSubclassStaticMethod             this call of the shared method is prone to copy paste errors     sharedStaticMethod  SubClass1 class getName                            other arguments          and this call is safe to copy paste     sharedStaticMethod  new Object       getClass   getEnclosingClass   getName                            other arguments

User · Answer

In order to support refactoring correctly  rename class   then you should use either    MyClass class getName       full name with package   or  thanks to  James Van Huis     MyClass class getSimpleName       class name and no more

User · Answer

Since the question Something like  this class  instead of  ClassName class   is marked as a duplicate for this one  which is arguable because that question is about the class rather than class name   I m posting the answer here   class MyService       private static Class thisClass   MyService class         or        private static Class thisClass   new Object       getClass   getEnclosingClass                static void startService Context context            Intent i   new Intent context  thisClass           context startService i             It is important to define thisClass as private because  1  it must not be inherited  derived classes must either define their own thisClass or produce an error message 2  references from other classes should be done as ClassName class rather than ClassName thisClass   With thisClass defined  access to the class name becomes   thisClass getName

User · Answer

I needed the class name in the static methods of multiple classes so I implemented a JavaUtil Class with the following method    public static String getClassName         String className   Thread currentThread   getStackTrace   2  getClassName        int lastIndex   className lastIndexOf           return className substring lastIndex   1       Hope it will help

User · Answer

If you want the entire package name with it  call   String name   MyClass class getCanonicalName      If you only want the last element  call   String name   MyClass class getSimpleName

[java] Getting the class name from a static method in Java

Conclusions

P.S.

Examples related to java

Examples related to static