I'm asking this question even though it has already been asked many times because I didn't find a solution after hours of searching.

I'm using Eclipse to learn Java. Last week everything worked properly. I could run whatever I wrote. Then today, I opened Eclipse, wrote some lines and when I tried to run it, I got an error:

```
Error: Could not find or load main class test.ArrayTest
Caused by: java.lang.ClassNotFoundException: test.ArrayTest

```

But that's not all : every project in my workspace is having the same issue. I can't run anything. At first I thought it was because I made a mistake at Eclipse start, so I closed it and re-opened it, but I was in the correct workspace.

I've tried to clean/rebuild it, doesn't work.  

I've tried to mess with Properties > Java Build Path, doesn't work.  

I've tried to create a new project with a simple 'Hello World', doesn't work.

```
package Hello;

public class Main
{
    public static void main(String[] args)
    {
        System.out.println("Hello World");
    }
}

```

[What I have in package explorer.](https://i.stack.imgur.com/Azbt7.png)

[Console display.](http://puu.sh/EIrT5/86516248bf.png)

The thing that suprises me the most is that I don't think I've done anything that can mess with Eclipse between the moment it was working and now. 

Does someone have another idea ?