在 STS/Eclipse 中找不到或加载主 class

Question

I have a main method in a package in one of my projects. Say, the package is com.ant.car . I am trying to run and/or debug this main method, and I keep getting the error Could not find or load main class com.ant.car .

I've searched this problem, and it seems like I can't figure out what is wrong.

1) I've checked run configurations. In Run->Run Configurations, I've checked that the Main class is com.ant.car.

2) I've checked build path. If I right click on the project, I select Build->Build Path, and under the Libraries tab I make sure there are no missing folders with red Xs next to them.

Not really sure what else to do. Any suggestions?

Answer 1

Project -> Clean

this is working

Answer 2

Try updating project by right clicking on it. Maven -> Update Project

Answer 3

Today I ran into the same problem and I tried a lot of answers. Nothing helped. Cleaning the project, build automatically is already checked, deleting .metadata , etc.

Eventually I tried this and it worked perfectly:

menu Project -> Properties
Java Build Path, tab Libraries

Remove the JRE System Library from there, press Add Library , take the JRE System Library and press Next . Workspace default JRE and press Finish .

Answer 4

What worked for me: Menu Project -> Properties In Java Build Path , tab Libraries Delete all libraries with a red [x] next to them.

In my case, problem happened when I switched from Kepler to STS IDE.

Answer 5

The solution to this was the following:

• Close Eclipse/STS
• Use a file explorer on your operating system to navigate to your workspace (In my case, I'm on Windows so I used Windows Explorer)
• Delete the .metadata directory (or to be safe, copy the directory somewhere else to be safe, then delete it)
• Restart Eclipse/STS

Is there a more improved answer than this? I don't want to look like I'm trying to boost my own reputation points, so if someone can provide a better answer then please do so.

Answer 6

Sometimes the problem can be caused by some newly added dependencies. Try removing the recently added jars. That's how I fixed my problem.

Answer 7

This issue occurs when the main .class file moved or not found because you changed the directory for committed/shared the project into the git or another repository.

To Resolve this issue --> Remove existing run configuration and new one. Find the parent pom.xml or project pom.xml and open cmd/command prompt and run the below commands,

1. mvn clean install package
2. mvn eclipse eclipse

Answer 8

It worked for me:
1. Delete metadata from work-space directory.
2. Import the project again, but selected copy to work-space option.

I think the cause for the error was Non-English characters in the original saved directory.

Answer 9

您只需要删除运行配置文件并重新启动 STS 并运行命令 -mvn clean install 并尝试重新启动服务

Answer 10

The Error "Could not find or load main class com.ant.car" occur when your class is not in build path. please make sure that .class file is generated and it's in build path ..

Answer 11

I faced the same issue..

just do follow these steps:

STS/Eclipse --> Project --> Enable "Build Automatically"

then refresh your project, it will resolve your issue.

Still not refreshed your projects automatically, just restart your STS and check.

Hope it will help you.

Answer 12

I think .class files are deleted/missing from JavaProject/bin folder.

To resolve this issue ->

1) Just cut paste and save the code contents of all the files that you are using then .class files will be regenerated.

2) Then run the code and you can see it works fine if there is no syntactical errors.

Answer 13

Project -> Clean... -> check project not working -> Clean

I already had build automatically set, but forcing STS to rebuild it fixed it.

Answer 14

1 ) Clean the Project
2 ) Enable build automatically Option
3 ) Update the maven project by use the short cut Alt + F5

Answer 15

手动删除目标文件夹和 mvn clean install 对我有用

Answer 16

A quick and easy fix is to directly run your SpringBootApplication class (ie Right click, Run As -> Spring Boot App). This runs the app and creates a run configuration automatically.

Answer 17

You can try one of the two solutions below: Solution 1 : Right click the project -> Gradle -> Refresh Gradle Project.

Solution 2 : Add gradle or maven in your environment variable. My problem was that I had not added gradle in my environment variable. Before, make sure Gradle or maven is installed in your OS.

Answer 18

我在这个问题上花了几个小时，最后通过这样做来修复它：属性 - > Java 编译器：取消选中复选框“使用'--release'选项”

Answer 19

This worked for me to solve the error. (I got this error after removing AWS ToolKit)

1. Close the Eclipse/ STS Eclipse.
2. Go to the WorkSpace folder.
3. Delete the .metadata folder.
4. Open the eclipse.
5. Run maven install on pom.
6. Run the project with your Run configuration.

Answer 20

1. Remove project from STS/Eclipse
2. Close or Refresh the Eclipse/ STS Eclipse.
3. Run maven install on pom.
4. Run the project with your Run configuration. Tried above mentioned steps to resolved issue.

Answer 21

I tried all the answers but finally what worked for me was deleting the project from eclipse workspace and importing it again.