空值的传递后判断为空的问题.

 

 

从页面接收到空值,(页面的空值null传到后台后变成字符串的"null")

客户系统接收到空值后一直报错,然后才发现切割字符串之前的判断一直是false

本人进过的测试:

System.err.println("customerIdStr:" + customerIdStr);

        System.out.println(customerIdStr == null);

        System.out.println(customerIdStr == "");

        System.out.println(customerIdStr == "null");

        System.out.println(customerIdStr == " ");

        System.out.println(customerIdStr == "null ");

 

        System.out.println(customerIdStr.equals(null));

        System.out.println(customerIdStr.equals(""));

        System.out.println(customerIdStr.equals("null"));只有本结果返回true

        System.out.println(customerIdStr.equals(" "));

        System.out.println(customerIdStr.equals("null "));

一般需要将明确的变量放到前面避免空指针异常,最近刚看阿里巴巴Java开发手册才注意到,在此说明一下.