Parameter implements Expression { public int hashCode() { return order; } Parameter(); void visit(ExpressionVisitor visitor); Class<?> typeConstraint(); Iterable<Expression> children(); int compareTo(Expression e); boolean equals(Object o); int hashCode();  }
@Test public void hashCodeDoesNotChange() { assertEquals(param.hashCode(), param.hashCode()); }
@Test public void hashCodeCanChange() { Parameter param2 = new Parameter(); assertNotEquals(param.hashCode(), param2.hashCode()); }