java Java在字符串中搜索浮点数
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Java searching float number in String
提问by Damian Drewulski
let's say i have string like that:
假设我有这样的字符串：
eXamPLestring>1.67>>ReSTOfString
示例字符串>1.67>>ReSTOfString
my task is to extract only 1.67 from string above.
我的任务是从上面的字符串中仅提取 1.67。
I assume regex will be usefull, but i can't figure out how to write propper expression.
我认为正则表达式会很有用，但我不知道如何编写正确的表达式。
回答by Ryan Amaral
If you want to extract all Int'sand Float'sfrom a String, you can follow my solution:
如果要从 a 中提取所有Int's和Float'sString，可以按照我的解决方案进行操作：
private ArrayList<String> parseIntsAndFloats(String raw) {
ArrayList<String> listBuffer = new ArrayList<String>();
Pattern p = Pattern.compile("[0-9]*\.?[0-9]+");
Matcher m = p.matcher(raw);
while (m.find()) {
listBuffer.add(m.group());
}
return listBuffer;
}
If you want to parse also negative valuesyou can add [-]?to the pattern like this:
如果您还想解析负值，您可以[-]?像这样添加到模式中：
Pattern p = Pattern.compile("[-]?[0-9]*\.?[0-9]+");
And if you also want to set ,as a separatoryou can add ,?to the pattern like this:
如果您还想设置,为分隔符，您可以,?像这样添加到模式中：
Pattern p = Pattern.compile("[-]?[0-9]*\.?,?[0-9]+");
.
.
To test the patterns you can use this online tool: http://gskinner.com/RegExr/
要测试模式，您可以使用此在线工具：http: //gskinner.com/RegExr/
Note: For this tool remember to unescape if you are trying my examples (you just need to take off one of the \)
注意：对于此工具，如果您正在尝试我的示例，请记住取消转义（您只需要取消其中一个\）
回答by Johan Sj?berg
You could try matching the digits using a regular expression
您可以尝试使用正则表达式匹配数字
\d+\.\d+
This could look something like
这可能看起来像
Pattern p = Pattern.compile("\d+\.\d+");
Matcher m = p.matcher("eXamPLestring>1.67>>ReSTOfString");
while (m.find()) {
Float.parseFloat(m.group());
}
回答by Nishant
String s = "eXamPLestring>1.67>>ReSTOfString>>0.99>>ahgf>>.9>>>123>>>2323.12";
Pattern p = Pattern.compile("\d*\.\d+");
Matcher m = p.matcher(s);
while(m.find()){
System.out.println(">> "+ m.group());
}
Gives only floats
只提供浮点数
>> 1.67
>> 0.99
>> .9
>> 2323.12
回答by Bohemian
Here's how to do it in one line,
这是在一行中完成的方法，
String f = input.replaceAll(".*?([\d.]+).*", "");
If you actually want a float, here's how you do it in one line:
如果你真的想要一个float，这里是你如何在一行中做到的：
float f = Float.parseFloat(input.replaceAll(".*?([\d.]+).*", "")),
回答by lpinto.eu
/**
* Extracts the first number out of a text.
* Works for 1.000,1 and also for 1,000.1 returning 1000.1 (1000 plus 1 decimal).
* When only a , or a . is used it is assumed as the float separator.
*
* @param sample The sample text.
*
* @return A float representation of the number.
*/
static public Float extractFloat(String sample) {
Pattern pattern = Pattern.compile("[\d.,]+");
Matcher matcher = pattern.matcher(sample);
if (!matcher.find()) {
return null;
}
String floatStr = matcher.group();
if (floatStr.matches("\d+,+\d+")) {
floatStr = floatStr.replaceAll(",+", ".");
} else if (floatStr.matches("\d+\.+\d+")) {
floatStr = floatStr.replaceAll("\.\.+", ".");
} else if (floatStr.matches("(\d+\.+)+\d+(,+\d+)?")) {
floatStr = floatStr.replaceAll("\.+", "").replaceAll(",+", ".");
} else if (floatStr.matches("(\d+,+)+\d+(.+\d+)?")) {
floatStr = floatStr.replaceAll(",", "").replaceAll("\.\.+", ".");
}
try {
return new Float(floatStr);
} catch (NumberFormatException ex) {
throw new AssertionError("Unexpected non float text: " + floatStr);
}
}
回答by Jesper Fyhr Knudsen
You can use the regex \d*\.?,?\d*This will work for floats like 1.0 and 1,0
您可以使用正则表达式\d*\.?,?\d*这将适用于 1.0 和 1,0 之类的浮点数
回答by LumenAlbum
Have a look at this link, they also explain a few things that you need to keep in mind when building such a regex.
看看这个链接，他们还解释了构建这样一个正则表达式时需要记住的一些事情。
[-+]?[0-9]*\.?[0-9]+
[-+]?[0-9]*\.?[0-9]+
example code:
示例代码：
String[] strings = new String[3];
strings[0] = "eXamPLestring>1.67>>ReSTOfString";
strings[1] = "eXamPLestring>0.57>>ReSTOfString";
strings[2] = "eXamPLestring>2547.758>>ReSTOfString";
Pattern pattern = Pattern.compile("[-+]?[0-9]*\.?[0-9]+");
for (String string : strings)
{
Matcher matcher = pattern.matcher(string);
while(matcher.find()){
System.out.println("# float value: " + matcher.group());
}
}
output:
输出：
# float value: 1.67
# float value: 0.57
# float value: 2547.758
