Optimize generated hashCode

The generated java hashCode method allocates an ArrayList then appends the fields to the list. Primitive fields will be boxed when added to the list.

The generated code shouldn't allocate a list or box primitives. The hashCode can be calculated by using a primitive int and some static utility methods which can return the hashCode for each type.

out << indent() << "@Override" << endl << indent() << "public int hashCode() {" << endl;
1839 indent_up();
1840 indent(out) << "List<Object> list = new ArrayList<Object>();" << endl;
1841
1842 for (m_iter = members.begin(); m_iter != members.end(); ++m_iter) {
1843 out << endl;
1844
1845 t_type* t = get_true_type((*m_iter)->get_type());
1846 bool is_optional = (*m_iter)->get_req() == t_field::T_OPTIONAL;
1847 bool can_be_null = type_can_be_null(t);
1848 string name = (*m_iter)->get_name();
1849
1850 string present = "true";
1851
1852 if (is_optional || can_be_null)

{ 1853 present += " && (" + generate_isset_check(*m_iter) + ")"; 1854 }

1855
1856 indent(out) << "boolean present_" << name << " = " << present << ";" << endl;
1857 indent(out) << "list.add(present_" << name << ");" << endl;
1858 indent(out) << "if (present_" << name << ")" << endl;
1859 if (t->is_enum())

{ 1860 indent(out) << " list.add(" << name << ".getValue());" << endl; 1861 }

else

{ 1862 indent(out) << " list.add(" << name << ");" << endl; 1863 }

1864 }
1865
1866 out << endl;
1867 indent(out) << "return list.hashCode();" << endl;
1868 indent_down();
1869 indent(out) << "}" << endl << endl;
1870 }