Error Main method not found in class MyClass please define the main method as

Question

New Java programmers often encounter these messages when they attempt to run a Java program     Error  Main method not found in class MyClass  please define the main method as     public static void main String   args  or a JavaFX application class must extend javafx application Application     Error  Main method is not static in class MyClass  please define the main method as     public static void main String   args      Error  Main method must return a value of type void in class MyClass  please define the main method as     public static void main String   args      java lang NoSuchMethodError  main Exception in thread  main      What does this mean  what can cause it  and what should one do to fix it

User · Answer

I feel the above answers miss a scenario where this error occurs even when your code has a main(). When you are using JNI that uses Reflection to invoke a method. During runtime if the method is not found, you will get a

java.lang.NoSuchMethodError: No virtual method

User · Answer

Generally  it means the program you are trying to run does not have a  main  method  If you are going to execute a Java program  the class being executed must have a main method   For example  in the file Foo java  public class Foo       public static void main final String args              System out println  hello              This program should compile and run no problem - if main was called something else  or was not static  it would generate the error you experienced   Every executable program  regardless of language  needs an entry point  to tell the interpreter  operating system or machine where to start execution  In Java s case  this is the static method main  which is passed the parameter args   containing the command line arguments  This method is equivalent to int main int argc  char   argv  in C language

User · Answer

When you use the java command to run a Java application from the command line  e g    java some AppName arg1 arg2       the command loads the class that you nominated and then looks for the entry point method called main  More specifically  it is looking for a method that is declared as follows   package some  public class AppName               public static void main final String   args               body of main method follows                       The specific requirements for the entry point method are    The method must be in the nominated class  The name of the method must be  main  with exactly that capitalization1  The method must be public  The method must be static 2  The method s return type must be void  The method must have exactly one argument and argument s type must be String   3       The argument may be declared using varargs syntax  e g  String    args   See this question for more information  The String   argument is used to pass the arguments from the command line  and is required even if your application takes no command-line arguments    If anyone of the above requirements is not satisfied  the java command will fail with some variant of the message   Error  Main method not found in class MyClass  please define the main method as     public static void main String   args  or a JavaFX application class must extend javafx application Application   Or  if you are running an extremely old version of Java   java lang NoSuchMethodError  main Exception in thread  main    If you encounter this error  check that you have a main method and that it satisfies all of the six requirements listed above     1 - One really obscure variation of this is when one or more of the characters in  main  is NOT a LATIN-1 character     but a Unicode character that looks like the corresponding LATIN-1 character when displayed   2 - Here is an explanation of why the method is required to be static   3 - String must correspond to java lang String and not to a custom class named String hiding it

User · Answer

If you are running the correct class and the main is properly defined  also check if you have a class called String defined in the same package  This definition of String class will be considered and since it doesn t confirm to main java lang String   args   you will get the same exception    It s not a compile time error since compiler just assumes you are defining a custom main method        Suggestion is to never hide library java classes in your package

User · Answer

Few min back i was facing   main method not defined  Now its resolved I tried all above thing but nothing was working There was not compilation error in my java file  I followed below things   simply did maven update in all dependent project  alt F5     Now problem solved Getting required result

User · Answer

The problem is that you do not have a public void main String   args  method in the class you attempt to invoke   It    must be static must have exactly one String array argument  which may be named anything  must be spelled m-a-i-n in lowercase    Note  that you HAVE actually specified an existing class  otherwise the error would have been different   but that class lacks the main method

User · Answer

The name of the exception suggests that the program tried to call a method that doesn t exist  In this context  it sounds like the program does not have a main method  though it would help if you posted the code that caused the error and the context in which the code was run   This might have happened if the user tried to run a  class file or a  jar file that has no main method - in Java  the main method is the entry point to begin executing the program   Normally the compiler is supposed to prevent this from happening so if this does happen  it s usually because the name of the method being called is getting determined ar run-time  rather than compile-time   To fix this problem  a new programmer must either add the midding method  assuming still that it s main that s missing  or change the method call to the name of a method that does exist   Read more about the main method here  http   csis pace edu  bergin KarelJava2ed ch2 javamain html

User · Answer

Other answers are doing a good job of summarizing the requirements of main   I want to gather references to where those requirements are documented   The most authoritative source is the VM spec  second edition cited    As main is not a language feature  it is not considered in the Java Language Specification    2 17 1 Execution - Virtual Machine Start-up 5 2 Virtual Machine Start-up   Another good resource is the documentation for the application launcher itself    java - the Java application launcher

[java] "Error: Main method not found in class MyClass, please define the main method as..."

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