问题
I am trying to run some java files in a new project. So I make the project, put the files in it and I try to run the main file so my game starts.
I get an error that says selection does not contain a main type.
I have tried several ways to run it:
- Some say to launch eclipse again, tried this a dozen times.
- Somewhere else someone pointed to open a new project and make a build path to the old project.
Didn't work either.
I am pretty sure it must work because I ran it a few hours ago at school. How do I get this working? Thank you in advance!
回答1:
Hope you are trying to run the main class in this way see screen shot:
If no then try this way and if yes then please make sure that your class you are going to run have main method i-e
public static void main(String[] args){ // some code here}
same definition. Hope this will help you.
回答2:
Right click on the folder where you put your main class then click on Build Path --> Use as Source Folder.
Finally run your main file as java application. Hope this problem will be solved.
回答3:
The other answers are all valid, however, if you are still having a problem you might not have your class inside the src folder in which case Eclipse may not see it as part of the project. This would also invoke the same error message you have seen.
回答4:
The entry point for Java programs is the method:
public static void main(String[] args) {
//Code
}
If you do not have this, your program will not run.
回答5:
I resolved this by adding a new source folder and putting my java file inside that folder. "source folder" is not just any folder i believe. its some special folder type for java/eclipse and can be added in eclipse by right-click on project -> properties -> Java buld path -> Source and add a folder
回答6:
Few things to check out:
- Do you have a main package? do all of your classes are under this package?
- Do you use a main class with public static void main(String[] args)?
- Do you declare: package ; in your main class?
- You can always clean the project before running it. In Eclipse - Just go to Project -> clean then run the app again.
回答7:
I ran into the same problem. I fixed by right click on the package -> properties -> Java Build Path -> Add folder (select the folder your code reside in).
回答8:
I am running eclipse from Ubuntu. Had this same problem and was able run the program through terminal. So I just moved the existing public static void main(String[] args) { just below the class declaration (it got automatically formatted by eclipse) and the next launch was successful. Then moved the main method back to where it was before and it worked fine this time.
回答9:
You must place all your files (file.java) under the root folder SRC.
回答10:
Put your Main Java class file in src/main/java folder and check if there is not any error in 'Java Build Path' by following right click on project and select Java Build Path->Source.
回答11:
I ran into the same issue and found that there was an extra pair of braces (curly brackets) enclosing public static void main(String args) { ... }. This method should really be at the top scope in the class and should not be enclosed around braces. It seems that it is possible to end up with braces around this method when working in Eclipse. This could be just one way you can see this issue when working with Eclipse. Happy coding!
回答12:
I had this happen repeatedly after adding images to a project in Eclipse and making them part of the build path. The solution was to right-click on the class containing the main method, and then choose Run As -> Java Application. It seems that when you add a file to the build path, Eclipse automatically assumes that file is where the main method is. By going through the Run As menu instead of just clicking the green Run As button, it allows you to specify the correct entry-point.
回答13:
When you save your file, make sure it has the extension .java. If it does not, Eclipse won't know to read it as a java file.
回答14:
Make sure the main in public static void main(String[] args) is lower case. For me it didn't work when I had it with capital letter.
回答15:
Right Click > Run AS > Run Configurations
In this screen if your "Main class" Text field is empty, then add the class name by clicking "Search" button on the right side of the text field and choose the class file. And then click "Run" button on the bottom of the configuration screen. That's it
回答16:
I had this problem in two projects. Maven and command line worked as expected for both. The problems were Eclipse specific. Two different solutions: Project 1): Move the main method declaration to the top within the class, above all other declarations like fields and constructors. Crazy, but it worked. Project 2): The solution for Project 1) did not remedy the problem. However, removing lombok imports and explicitly writing a getter method solved the problem
Conclusion: Eclipse and/or the lombok plugin have/has a bug.
回答17:
If you are working with a Maven project you have to understand the fact that directory layout is bit different. In this the package name must be src/main/java.
For this update your source folder by right click on project root folder -> properties -> java build path -> source tab. Here remove all other source folders as they might have been added in wrong manner. Now, select project /src/main/java as the source folder. Add and apply the changes. Now refresh your workspace using F5.
This should fix the issue of not recognizing a main type.
来源：https://stackoverflow.com/questions/16225177/error-selection-does-not-contain-a-main-type