从 java jtextfield 读取双精度
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read in double from java jtextfield
提问by lecardo
Seems like a very simple question however I can't read in a double from a jtextfield. I can easily read in a string using getText(); but no luck with double.
似乎是一个非常简单的问题，但是我无法从 jtextfield 中读取 double。我可以使用 getText() 轻松读取字符串；但没有运气双。
My objective is read in the double carry out a subtraction on it and then redisplay it back to the user once the submit buttons pressed...Action listener is working fine and to make it look more simple I didn't add it in...if it helps I can add it.
我的目标是在 double 中读取并对其进行减法，然后在按下提交按钮后将其重新显示给用户......动作侦听器工作正常，为了使它看起来更简单，我没有将它添加进去.. .如果有帮助，我可以添加它。
if (e.getSource() == submit)
{
cashRecieved = CashNeeded.getText();
}
cashRecieved is type double therefore eclipse is complaining understandable stating it can't store a string to a double....
cashRecieved 是 double 类型，因此 eclipse 抱怨说它无法将字符串存储为 double 是可以理解的....
采纳答案by Vineet Kosaraju
You need to convert the String into a double. To do this, use the parseDouble method:
您需要将字符串转换为双精度。为此，请使用 parseDouble 方法：
cashRecieved = Double.parseDouble(CashNeeded.getText());
This returns type double (primitive), whereas valueOf returns type of the class Double.
这将返回 double（原始）类型，而 valueOf 返回 Double 类的类型。
EDIT:
编辑：
As Ingo mentioned, you should make sure you take care of the NumberFormatExceptions that occur when you try to parse an invalid string (eg: "Hello123") into a number.
正如 Ingo 所提到的，您应该确保处理在尝试将无效字符串（例如：“Hello123”）解析为数字时发生的 NumberFormatExceptions。
try {
cashRecieved = Double.parseDouble(CashNeeded.getText());
} catch (NumberFormatException e) {
e.printStackTrace();
// handle the error
}
回答by Blub
double d = Double.valueOf(CashNeeded.getText());
You shouldn't capitalize variable names (I assume CashNeeded is one).
您不应该将变量名称大写（我假设 CashNeeded 是其中之一）。
