Strange class that compiled with JDK 9, but not 1.6, 1.7 nor 1.8.

One.java

/**
 * As seen on https://javaspecialists.slack.com/messages/general 
 *
 * This class fails to compile with JDK 1.6, 1.7 and 1.8:
 *
 * class Two extends Observable {	// Nothing special about the choice of Observable here
 *                   ^
 *   symbol: class Observable
 * 1 error
 *
 * It does compile with JDK 9 even with the -source 1.8 -target 1.8 flags.  If we change
 * the order of the imports and put the "import static" after the normal import, it 
 * compiles in all JDK versions.  IDEs usually reorder these imports automatically, which
 * is why you might not have seen this compiler error.  We would have thought that it 
 * didn't matter.
 *
 * Survey results:
 * ===============
 * 18% said "static imports first", which makes javac unhappy
 * 24% said "static imports last", which is correct
 * 52% said "Compiler doesn't care".  That's what I would've answered too, but as we
 *     see in the code example, javac /does/ care.  IMHO it shouldn't.  Fixed in JDK 9.
 * 6% said "I know how to fix that..." - perhaps they knew about javac in JDK 9?
 *
 * I would say that at least 70% were incorrect.  Amazing how IDEs have made our brains
 * switch off.  And with Apple removing the Esc key, who will be using VIM in future?
 *
 * @author Tom Gutteridge, Heinz Kabutz
 */
package whatever;

import static whatever.Two.CONSTANT;

import java.util.Observable;

public class One {
	int blah = CONSTANT;	// Just so there's some point in the static import
}

class Two extends Observable {	// Nothing special about the choice of Observable here
	static final int CONSTANT = 123;
}