试了下，执行成功，没报错。on eclipse (myeclipse)

```java
public class GeneratorTest {

public static void main(String[] args) {
String[] strings = FArray.fill(new String[1], new RandomGenerator.String());
for (String s : strings)
System.out.println(s);

Integer[] integers = FArray.fill(new Integer[1], new RandomGenerator.Integer());
for (Integer i : integers)
System.out.println(i);
}

static class FArray {
public static <T> T[] fill(T[] a, Generator<T> gen) {
for (int i = 0; i < a.length; i++)
a[i] = gen.next();
return a;
}
}

static interface Generator<T> {
public default T next() {
return null;
}
}

static class RandomGenerator {
public static class String implements Generator<java.lang.String> {
}

public static class Integer implements Generator<java.lang.Integer> {
}
}

}
```