### Question:
Kleene extends ERE { @Override public String toString() { return children.get(0) + "*"; } private  Kleene(ERE child); static ERE get(ERE child); @Override EREType getEREType(); @Override String toString(); @Override ERE copy(); @Override boolean containsEpsilon(); @Override ERE derive(Symbol s);  }### Answer:
@Test public void testString() { assertEquals("a*", aStar.toString()); }