java - 检查输入空

Question

我发现如果输入不是数字，这行代码会出错

int sum = Integer.parseInt(request.getParameter("sum"));

错误信息是

type Exception report

message

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: java.lang.NumberFormatException: For input string: "a"
root cause

java.lang.NumberFormatException: For input string: "a"

如果输入是字符串或null，如何处理输入？

谢谢

Answer 1

您应该首先确保请求参数不为空且仅包含数字，使用:

if (request.getParameter("sum") != null &&
    request.getParameter("sum").matches("^\\d+$"))
    int sum = Integer.parseInt(request.getParameter("sum"));