public static String getString(Object obj) {
        if (obj == null) {
            return null;
        }

        if (obj instanceof String) {
            return (String) obj;
        }

        return obj.toString();
    }
Convert val to specified numeric type
Date: 2017/4/21
Company: www.dtstack.com
@author xuchao
core/src/main/java/com/dtstack/flink/sql/util/MathUtil.java