Static nested class in Java, why?

public class LinkedList<E> ... {
...

 private static class Entry<E> { ... }

}

package test;

public class UpperClass {
public static class StaticInnerClass {}

public class InnerClass {}

public static void main(String[] args) {
	// works
	StaticInnerClass stat = new StaticInnerClass();
	// doesn't compile
	InnerClass inner = new InnerClass();
}
}