static public PrefixOperator createPrefixOperator(final String operatorStr, final String headStr, final int precedence) { PrefixOperator oper; if (headStr.equals("PreMinus")) { oper = new PreMinusOperator(operatorStr, headStr, precedence); } else if (headStr.equals("PrePlus")) { oper = new PrePlusOperator(operatorStr, headStr, precedence); } else { oper = new PrefixOperator(operatorStr, headStr, precedence); } return oper; }