sclass JE_RepElement<A> extends JEInstantCompressor_AnyType<L<A>> {
  scaffolded public IJavaExpr compress(L<A> data) {
    bool sc = scaffoldingEnabled(this);
    if (empty(data)) null;
    A a = first(data);
    int n = l(data);
    for (int i = 1; i < n; i++)
      if (!eq(data.get(i), a)) {
        if (sc) scaffoldCalled(this, "diff at " + i + "/" + n);
        null;
      }
    ret javaExpr(
      functionCall repSimple(n, elementToJava(a)),
      -> repSimple(n, a));
  }
  
  swappable IJavaExpr elementToJava(A o) {
    var e = javaObjectToIJavaExpr(o);
    if (e == null) fail("elementToJava: " + className(o));
    ret e;
  }
}