Troubleshooting Eclipse

Error when compiling from the ant build.xml file in Eclipse

BUILD FAILED
C:\Users\Eli\Documents\openmrs-trunk\build.xml:150: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre8"

Solution

copy C:\Program Files\Java\jdk1.8.0_172\lib\tools.jar to C:\Program Files\Java\jre8\lib\ext

A cycle was detected in the build path of project

This error appears in the Eclipse Problems tab and will not go away.

Solution

Its a bug. Tell Eclipse to not throw an error about that:
Window ⇒ Preferences ⇒ Java ⇒ Compiler ⇒ Building
And set Circular Dependencies to Warning or Ignore