I am using NetBeans IDE and have created a new project. The new project includes a Main.java.
Is it necessary to have it named Main.java, or can I rename the Main.java into another name? If so, how can I do this? When I try to right-click Main.java, there is no rename option. I thought it was possible.
There should be a menu item called
Refactor --> Rename
Link from NetBeans Wiki
Your name can be anything, as long as you have a
public static void main(String[] args)
in it (This is only if you want this class to be the entry point when you run your application).
You can call the file <whatever you like>.java, but the name of the class in that file must match the new name you give to the file.
So if you rename the file to MyCoolClass.java, you also have to change the class from public class Main to public class MyCoolClass.
you can even have the simpler way,click on the file_name.java in the Projects panel,wait for a sec and click one more time (just as you rename any other folder/file).It will allow you to replace the new name and then it will popup a window asking whether you want to refactor or not...
you got to use the refractor, as it is the safest way to do such actions
Related
In new Interface package when I right-click in new java class option nit shown
interface is not a valid package name, because it is a Java keyword. A keyword can not be used as an identifier, for example as a package name, variable name or class name. If you choose a different name for your package, the option to create a Java class should appear.
Make sure you have created the module of the Java type.
To readers who like this question: I asked this question eight years ago (as of 2022) and there are only three upvotes. Please be aware that there are not many of us who need this feature and it is unlikely this will be supported by IntelliJ (or any modern IDE) for the foreseeable future.
When I use IntelliJ to copy a package which contains subpackages, every internal references to other classes in the same package is converted to an ugly fully-qualified name. Worse yet, this fully-qualified name links back to the old package instead of to the copied class in the new package! Does anyone know a workaround for this problem?
To reproduce this problem, I create a project structure like this:
Where A.java is:
package example;
public class A { }
And B. java is:
package example;
public class B {
private A a;
public B(A a) {
this.a = a;
}
}
I then Ctrl-C and Ctrl-V the example folder, and edit the dialog as below:
The copied version of classB now has every instance of A replaced with example.A
package example2;
import example.*;
public class B {
private example.A a;
public B(example.A a) {
this.a = a;
}
}
Does anyone have a suggested work-around to avoid this behavior, and simple change the package name, leaving everything else alone? Thanks!
P.S. While version control is usually the best way to track different versions of a program, I want to create an actual copy in this case. I use IntelliJ for teaching programming, and I create multiple versions of small, multi-packaged programs demonstrating how the program improves as I model refactoring techniques.
[Reported on Jet Brains here] 3.
You can try this:
Select class A and class B in the Project Structure;
Press F5;
In opened window enter new path, for example, C:\projects\other\src\example2;
Click Ok.
My latest workaround:
Set up IntelliJ to show excluded packages
Exclude the package to be copied (e.g. example)
Rename the package to be copied to a temporary name (e.g. example_temp). Ignore the warning about names not being updated.
Copy the package into the src folder. Rename it to the original name (e.g. example) during the copy. Since the original name is no longer excluded, the package will reappear.
Rename the copy to the new name. (e.g. rename example to example_v2)
Rename the temporary file back to the original (e.g. rename example_temp to example)
Remove the exclusion on the original directory (e.g. right-click example_temp->Mark directory as->Cancel Exclusion.)
Nothing of these were helpful for me, but I found a 100% working method. I had a structure like this:
package hometask1,
package hometask2,
package hometaskN,
where each next package has the previous package's classes as a base and has some new features with some classes changed. When I copied the previous package hometask(N-1) to the next hometaskN, it would have the previous package's (hometask(N-1)) import statements. I found that I have solved my problem following these steps:
Add new (temporary) project.
Create package with name equals previous package (for example, hometask1).
Copy classes from old project hometask1 to temp project hometask1.
Create package with necessary name in temporary project (for example, hometask2).
Move (not copy) all included packages and classes from temp hometask1 to temp hometask2. All imports are correct now.
Create in old project package with same name (hometask2).
Move or copy classes from temp hometask2 to main project hometask2.
Done.
Try copy/paste using the mouse. This method is slow but works.
1. Open the dir. you want to copy from.
2. Click on the class you want to copy.
3. Copy it.
4. In the new package, click on the dir where you need to put the class.
5. Click paste.
You may also need to update the imports to reflect the new dir.
Here is an effortless way (which works for sub packages that are in the same project or in different projects). Suppose we want to copy from Project1 to Project2 and we have the following structure (i.e. we want to copy the Car and Main classes in SubPackage21):
Project1
Package1
SubPackage11
Car.java
Main.java
Project2
Package2
SubPackage21
Step 1
Right-click on SubPackage21, click "Show in Explorer", and copy the path. It will be something like "...\Package2".
Step 2
Click on SubPackage11, press F5, paste the path and press "Enter".
You will get the following:
Project2
Package2
SubPackage21
SubPackage11
Car.java
Main.java
Step 3
Drag and drop the classes from SubPackage11 to SubPackage21, and press "Refactor" for all of them (this way the package name is replaced with the correct one, and no strange imports are added).
The error states Error main method not found in class. Please define the main method as:
public static void main(String[] args).
Eclipse was working for me a few days ago, but now it just gives me that message
an example would be
public class Test {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("Hello World");
}
}
Check if exists any error in your project. Not just the compilation errors. Click on project and check the "Problems" view in Eclipse. You need to remove all of "Errors".
First clean your project Using Project-->Clean and then build it again.
Also make sure that your build path is properly set.
I ran into the same issue. Just clean your project..save your project and then run it.
Check whether you have created a class with the name "String". If you have created a class with the name "String", the compiler will not be able to resolve the conflict between 2 classes i.e. java.lang.String and your String class therefore it won't recognize the main method.
So just remove that String class or rename it.It happened to me also.. I resolved using this only.
I ran into this problem also when I moved the location of the main method in my program to another file in the same program. If this is what happened to you, the fix is to go to the top of Eclipse near the bug and play icons and change the "Run as..." field to "Java application" from whatever its previous location was.
Try to resturt Eclipse in a new workspace.
Maybe you are creating 2 classes in the same package or u have defined one of your defined class name as "String". If you have then change that classname to something else , because at that time compiler cannot differentiate between java.lang.String and your user defined class "String". So jst chage the name of that String class.
I have downloaded a huge project written in Java. I wish to know the Classes and Methods of every class that are available in the project (for further analysis). How can I recover this information. Can I try javadoc in eclipse?
I guess you may ask about changing SVN properties.
Follow this step if that so.
press Alt + Shift + Q
Select Show view (view : Outline)
then under that u can see all details
I have wrote a custom doclet to list the classname and its methods:
public class ListClassAndMethods {
public static boolean start(RootDoc root) {
ClassDoc[] classes = root.classes();
for(ClassDoc clazz : classes){
System.out.println("Class Name: "+clazz);
System.out.println("--------------------------");
for(MethodDoc methodz :clazz.methods()){
System.out.println(methodz.name());
}
}
return true;
}
}
you need to run create a jar of this class and refer it while creating
a javadoc using Eclipse IDE
I would extract all the class source files (.java) with find (if you're on a *nix implementation) and create an empty NetBeans project with just one package and all the classess inside it. Netbeans will correct the package declaration and you can easily use autogenerate javadoc to get a navigable web archive listing all the classes and public/protected methods.
Of course the code may not run anymore but you'll get what you want in minutes.
class HelloObject {
void speak() {
System.out.println("Hello (from object)!");
}
}
class HelloTester {
public static void main(String[] args) {
HelloObject object = new HelloObject();
object.speak();
}
}
When I change the "HelloTester" class name to something like "HelloTester2", the program suddenly works. The class file is called ClassesBegin.java.
Why does the java program not work when I try to change the name of the class?
EDIT: Sorry I should have clarified more. I changed the class name to HelloTestera and this is the error I get:
Exception in thread "main" java.lang.NoClassDefFoundError: HelloTester
But it works even when the file name has nothing to do with a class name. It works with HelloTester when the file name is ClassesBegin.java
You need to change the file name, not just the class name.
In Java, the .java and .class names have to be identical to the class name.
Hence, each class has to go to a separate file with its name so that a separate .class file is created.
Putting two different classes in the same file is a C++ practice that works with its compilation model, not with Java.
Edit: User ended up clarifying what caused his error, so obviously my answer here is not relevant. All the above applies to public classes. You can pull that off for package-level classes though I have to say that I consider that a horrible practice. If you're going to have something used by multiple classes in your package, give it its own file. If it's used just by one class, make it an inner class...
"EDIT: Sorry I should have clarified more. I changed the class name to HelloTestera and this is the error I get: Exception in thread "main" java.lang.NoClassDefFoundError: HelloTester But it works even when the file name has nothing to do with a class name. It works with HelloTester when the file name is ClassesBegin.java"
The file name and the class name must match if the class is public.
If you chagned the class name to "HelloTestera" but ran "java HelloTester" (which is what java.lang.NoClassDefFoundError: HelloTester would indicate) then the issue is that you passed the wrong class name to "java".
But save yourself a lot of time and name the class and the file the same thing and keep it at one top level class per file. A simple way to "force" that is to make all of your classes public for now (you can only have one public class per file). This will really save you from making some mistakes.
You are allowed to have as many non-public classes in your ClassesBegin file as you like in terms of compilation. But only the public (ClassesBegin in this case; until you change the name of the file) is able to be used externally.
In particular, the main() method must be public, and in a public class to be able to be found by java. Rename your file to HelloTester to make it work.
Or - rename the HelloTester class in your IDE, which probably is relaming the file automatically, since it has a main method, and the IDE knows that it needs to be the public class...
The easiest way to do this is:
1) only one top level class per file
2) the name of the class and the name of the file must match (name and CasE)
This makes it easier to find you classes (the name of the class is the name of the file) and you don't wind up with some odd issues where the compielr cannot find all of the classes to copmpile.
Java also has a restriction where the name of a public class 100% must be the same as the name of the file. The restriction is only on public classes (or interfaces or enums). You can have as many non-public types as you want in a file... but don't do that - stick with one top level class/interface/enum per file.
You write:
I changed the class name to HelloTestera and this is the error I get: Exception in thread "main" java.lang.NoClassDefFoundError: HelloTester
It seems you are not actually running the renamed class but the old one. Did you call Java with the new changed class name? Did you recompile the file before running the class?
After renaming the class, you should first run:
javac ClassesBegin.java
And then:
java HelloTestera
Which for me yields:
Hello (from object)!
Usually, when using an IDE, these issues are handled for you (compile before running).