This is happening when you click to start JDeveloper. It throws this error and fails to start it.
The amount of RAM allocated for JDeveloper's JVM is more than your system can provide and as a result JDeveloper will not start.
Solution:
Reduce the RAM. Check my previous blog post "TROUBLESHOOTING: "Low Memory Warning" of JDeveloper or How to tweak memory settings." on how to do it
Reduce the RAM. Check my previous blog post "TROUBLESHOOTING: "Low Memory Warning" of JDeveloper or How to tweak memory settings." on how to do it