使用 Java 和 HTML 获取两个字符串输入总和的正确方法是什么？
[英]What is the correct way to get the sum of two string inputs using Java with HTML?
问题描述
I am attempting to make an HTML page where the user inputs 2 numbers as strings, clicks submit, and the sum is displayed.
我正在尝试制作一个 HTML 页面，其中用户输入 2 个数字作为字符串，点击提交，然后显示总和。 I screwed up something along the way while parsing and I am not sure how to correct it.我在解析过程中搞砸了一些东西，我不知道如何纠正它。 How do I fix this issue?我该如何解决这个问题？
java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1838)
java.base/jdk.internal.math.FloatingDecimal.parseFloat(FloatingDecimal.java:122)
java.base/java.lang.Float.parseFloat(Float.java:461)
basicaddition.BasicAddition.processRequest(BasicAddition.java:42)
The code:编码：
String EmptyError = "";
String FirstNumber = request.getParameter("FirstNumber");
String SecondNumber = request.getParameter("SecondNumber");
float firstNumber = Float.parseFloat(FirstNumber);
float secondNumber = Float.parseFloat(SecondNumber);
if(FirstNumber.isBlank() && SecondNumber.isBlank())
{
EmptyError = "There is no sum";
}
else {
try {
firstNumber = Float.parseFloat(FirstNumber);
} catch (NumberFormatException ex) {
EmptyError = "Value is not a number";
}
try {
secondNumber = Float.parseFloat(SecondNumber);
} catch (NumberFormatException ex) {
EmptyError = "Value is not a number";
}
}
Float Result = firstNumber + secondNumber;
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
/* TODO output your page here. You may use following sample code. */
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet BasicAddition</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Returns the sum of two numbers, ");
out.println("</h1>");
out.println("<input type='text' name='FirstNumber' />");
out.println(EmptyError);
out.println("<input type='text' name='SecondNumber' />");
out.println(EmptyError);
out.println("<input type='submit' value='Get the sum' />");
out.println(EmptyError);
out.println(Result);
out.println("<h1>Servlet BasicAddition at " + request.getContextPath() + "</h1>");
out.println("</body>");
out.println("</html>");
2 个解决方案
解决方案1
0 2020-02-06 01:19:00
I'm seeing you're trying to parse the numbers before the condition!我看到您正在尝试在条件之前解析数字！
float firstNumber = Float.parseFloat(FirstNumber);
float secondNumber = Float.parseFloat(SecondNumber);
Those two lines throw an exception because FirstNumber and SecondNumber are not a valid number!这两行抛出异常，因为 FirstNumber 和 SecondNumber 不是有效数字！
解决方案2
0 2020-02-06 04:33:50
In your if condition, you have to use 'OR' operator.在您的if条件下，您必须使用“OR”运算符。 Otherwise at least one condition is false it jumps to else .否则至少有一个条件为false它跳转到else 。 you have to remove String to float conversion before the if statement.您必须在if语句之前删除String以进行float转换。 Check below code:检查以下代码：
String EmptyError = "";
String FirstNumber = request.getParameter("FirstNumber");
String SecondNumber = request.getParameter("SecondNumber");
float firstNumber, secondNumber;
if (FirstNumber.isBlank() || SecondNumber.isBlank()) {
EmptyError = "There is no sum";
} else {
//Rest of the code
}
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