Java searching float number in String

Question

let's say i have string like that:

eXamPLestring>1.67>>ReSTOfString

my task is to extract only 1.67 from string above.

I assume regex will be usefull, but i can't figure out how to write propper expression.

Answer 1

If you want to extract all Int's and Float's from a String, you can follow my solution:

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 values you can add [-]? to the pattern like this:

    Pattern p = Pattern.compile("[-]?[0-9]*\\.?[0-9]+");

And if you also want to set , as a separator you can add ,? to the pattern like this:

    Pattern p = Pattern.compile("[-]?[0-9]*\\.?,?[0-9]+");

.

To test the patterns you can use this online tool: 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 \)

Answer 2

You could try matching the digits using a regular expression

\\d+\\.\\d+

This could look something like

Pattern p = Pattern.compile("\\d+\\.\\d+");
Matcher m = p.matcher("eXamPLestring>1.67>>ReSTOfString");
while (m.find()) {
    Float.parseFloat(m.group());
}

Answer 3

Here's how to do it in one line,

String f = input.replaceAll(".*?(-?[\\d.]+)?.*", "$1");

Which returns a blank String if there is no float found.

If you actually want a float, you can do it in one line:

float f = Float.parseFloat(input.replaceAll(".*?(-?[\\d.]+).*", "$1"));

but since a blank cannot be parsed as a float, you would have to do it in two steps - testing if the string is blank before parsing - if it's possible for there to be no float.

Answer 4

    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

>> 1.67
>> 0.99
>> .9
>> 2323.12

Answer 5

You can use the regex \d*\.?,?\d* This will work for floats like 1.0 and 1,0

Answer 6

Have a look at this link, they also explain a few things that you need to keep in mind when building such a regex.

[-+]?[0-9]*\.?[0-9]+

example code:

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:

# float value: 1.67
# float value: 0.57
# float value: 2547.758

Answer 7

/**
 * 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);
    }
}