我如何在 Java 中读取双精度值？
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How do I read in a double in Java?
提问by Jeff
I am trying to get a decimal input from the keyboard, and it is just not working. First I tried
我正在尝试从键盘获取十进制输入，但它不起作用。首先我试过
double d = Integer.parseInt(JOptionPane.showInputDialog(
"Please enter a number between 0 and 1:"));
and that obviously didn't work very well.
这显然效果不佳。
I am used to just parsing int's as they come in from the keyboard right into a variable, but I don't know what I am supposed to do for decimals! I need to be able to take a decimal like .9 straight from the keyboard and be able to have it in a variable I can do calculations with.
我习惯于将 int 从键盘传入时解析为变量，但我不知道我应该为小数做什么！我需要能够直接从键盘上取一个像 0.9 这样的小数，并且能够将它放在一个我可以用来计算的变量中。
I know this is a basic question, but I need some help. Thanks!
我知道这是一个基本问题，但我需要一些帮助。谢谢！
采纳答案by Avindra Goolcharan
double d = new Double(JOptionPane.showInputDialog("Please enter a number between 0 and 1:"));
回答by John Weldon
回答by Tim
Have you tried substituting Doublefor Integer?
您是否尝试过替代Double的Integer？
So Double.parseDouble(JOptionPane.showInputDialog("Please enter a double:"));http://java.sun.com/javase/6/docs/api/java/lang/Double.html#parseDouble(java.lang.String)
所以Double.parseDouble(JOptionPane.showInputDialog("Please enter a double:"));http://java.sun.com/javase/6/docs/api/java/lang/Double.html#parseDouble(java.lang.String)
Or Double.valueOf(JOptionPane.showInputDialog("Please enter a double:"))http://java.sun.com/javase/6/docs/api/java/lang/Double.html#valueOf(java.lang.String)
或者Double.valueOf(JOptionPane.showInputDialog("Please enter a double:"))http://java.sun.com/javase/6/docs/api/java/lang/Double.html#valueOf(java.lang.String)
回答by Pascal Thivent
You should use Double.parseDouble(String). Another option is Double.valueOf(String)and I prefer the later because it's more change tolerant (if the parameter is changed for something else than a String, you may not have to modify your code), even if it creates an unnecessary Doublethat you don't need in your example.
你应该使用Double.parseDouble(String). 另一种选择是Double.valueOf(String)，我更喜欢后者，因为它更能容忍变化（如果参数更改为 a 以外的其他内容String，您可能不必修改代码），即使它创建了Double您在示例中不需要的不必要的代码.
