I'm using Eclipse(4.9.0) on my MacBook (High Sierra, Java 11) and this error is showing sometimes, if I'm on another app, the errors create a "stack" as you see in the screenshot, it is annoying to come back to Eclipse and to close this error every time. Can somebody help me solve this?
This indeed seems to be an issue when Eclipse is run with Java 11. I have created Bug 539545 to report this.
In the meantime, you can work around this issue by disabling news feed polling. To do so, go to Preferences... -> General -> News, and untick the Enable automatic news polling option:
The error window will no longer appear.