The public type classname must be defined in its own file error in Eclipse

Question

I have written the following code   package staticshow    public class StaticDemo     static int a   3    static int b   4     static       System out println  Voila  Static block put into action           static void show         System out println  a      a       System out println  b      b          public class StaticDemoShow     public static void main         StaticDemo show             I am getting the error message   The public type StaticDemo must be defined in its own file   error in the very first line public class StaticDemo    Why is it happening and how can I resolve it  Note that my project name is StaticDemoShow  package name is staticshow and class names are as given in the code   EDIT- After making just one class public or both the classes default  I am getting the error  Selection does not contain a main type   Now what should I do

User · Answer

error in the very first line public class StaticDemo {

Any Class A which has access modifier as public must have a separate source file as A.java or A.jav. This is specified in JLS 7.6 section:

If and only if packages are stored in a file system (§7.2), the host system may choose to enforce the restriction that it is a compile-time error if a type is not found in a file under a name composed of the type name plus an extension (such as .java or .jav) if either of the following is true:

The type is referred to by code in other compilation units of the package in which the type is declared.

The type is declared public (and therefore is potentially accessible from code in other packages).

However, you may have to remove public access modifier from the Class declaration StaticDemo. Then as StaticDemo class will have no modifier it will become package-private, That is, it will be visible only within its own package.

Check out Controlling Access to Members of a Class

User · Answer

Java rule   One public class in one file

User · Answer

You can t use 2 public class instances  you need to use one  Try using class  name  instead of public class  name

User · Answer

I had two significant errors in my program  From the other answers  I learned in a single java program  one can not declare two classes as  public   So I changed the access specifier  but got another error as added to my question as  EDIT  that  Selection does not contain a main type   Finally I observed I forgot to add  String args    part in my main method  That s why the code was not working  After rectification  it worked as expected

User · Answer

If  java file contains top level  not nested  public class  it have same name as that public class  So if you have class like public class A      it needs to be placed in A java file  Because of that we can t have two public classes in one  java file   If having two public classes would be allowed then  and lets say aside from public A class file would also contain public class B   it would require from A java file to be also named as B java but files can t have two  or more  names  at least in all systems on which Java can be run    So assuming your code is placed in StaticDemoShow java file you have two options    If you want to have other class in same file make them non-public  lack of visibility modifier will represent default package-private visibility    class StaticDemo      It can no longer public      static int a   3      static int b   4       static           System out println  Voila  Static block put into action               static void show             System out println  a      a           System out println  b      b             public class StaticDemoShow      Only one top level public class in same  java file     public static void main             StaticDemo show             Move all public classes to their own  java files  So in your case you would need to split it into two files    StaticDemo java  public class StaticDemo      Note  same name as name of file      static int a   3      static int b   4       static           System out println  Voila  Static block put into action               static void show             System out println  a      a           System out println  b      b             StaticDemoShow java  public class StaticDemoShow        public static void main             StaticDemo show

User · Answer

Cant have two public classes in same file     public class StaticDemo    Change to     class StaticDemo

User · Answer

Save this class in the file StaticDemo java  Also you cant have more than one public classes in one file

User · Answer

You can have only one public class in a file else you will get the error what you are getting now and name of file must be the name of public class

[java] "The public type <<classname>> must be defined in its own file" error in Eclipse

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