Question

I keep getting this error here:

SEVERE: java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:504)
at java.lang.Integer.parseInt(Integer.java:527)
at com.myapp.cmt.web.ContentController.saveContent(ContentController.java:129)

It happens when no options are selected on the dropdown menu for categories on my page. I’m checking the length, so how come it’s still trying to process the parseInt()?

        String[] category = request.getParameterValues("categories");
        if (category.length > 0) {
            content.addCategory(contentDao.findCategory(Integer.parseInt(category[0])));
        }

My HTML

    <strong>Category</strong><br/>
    <select name="categories">
        <option></option>
    <c:forEach items="${categories}" var="category">
        <option value="${category.id}" <c:if test="${content.hasCategory(category)}"> CHECKED</c:if>>${category.name}</option>
    </c:forEach>
    </select>

Answer 1

The length of your array is only half the story… you have to also check what’s in the array. Try some code like this:

if (category.length > 0 &&
  category[0] != null &&
  category[0].trim().length() > 0)
    content.addCategory(contentDao.findCategory(Integer.parseInt(category[0])));
}