从逗号sep属性列表创建数组的更优雅的解决方案？

Question

In my properties file I have one property, which contains a comma separated list of values

In my code, I would like to load that property in, split it from the commas, and add each value into an array. I also want to make sure I don't have values in the array due to whitespace etc

example property :

prop_allowed_extensions = .jpeg,tiff, .txt 

I have come up with this so far, but it feels dirty, is there a more elegant solution?

String test = classProperties.getProperty("prop_allowed_extensions", "txt, jpeg");
String[] splitString = StringUtils.split(test, ',');
String[] newString = new String[splitString.length];             
for (int i = 0; i < splitString.length; i++)
{
   newString[i] = StringUtils.trim(splitString[i]);                
}

I just want the text of the file extension, would it be appropriate to use a regular expression to remove whitespace/non-letters?

Answer 1

Apache Jakarta Commons Configuration handles properties file in a clean way, allowing you to specify lists in different formats:

colors.pie = #FF0000, #00FF00, #0000FF

OR

colors.pie = #FF0000;
colors.pie = #00FF00;
colors.pie = #0000FF;

And get the list like this:

String[] colors = config.getStringArray("colors.pie");
List colorList = config.getList("colors.pie");

See the How-to

Answer 2

You can do it in two steps:

String[] allowedExtensions = str.replaceAll("[^\\w,_]", "").split(",")

(First kill anything that is not either a comma, an underscore or a word character (letter or digit), then split the resulting string

Answer 3

I'd personally just reduce it to the following (keeping in mind that String.split() takes a regular expression), but I don't know whether or not you'd consider it more elegant:

String test = classProperties.getProperty("prop_allowed_extensions",
        "txt, jpeg");
String[] extensions = test.trim().split("\\s*,\\s*");

Edit : You can remove the leading dot on each extension too, if it is present (this, or one of several other ways):

String[] test = classProperties.getProperty("prop_allowed_extensions",
        "txt, jpeg").trim().split("^\\.", 2);
String[] extensions = test[test.length - 1].split("\\s*,\\s*.?");

Answer 4

Following your pattern, you can do it like this:

String test = classProperties.getProperty("prop_allowed_extensions", "txt, jpeg");
List<String> extensions = new ArrayList<String>();         
for (String part:test.split(",")) {
   extensions.add(part.trim());               
}

The difference is that the result is in a list now. test.split(",") will be called only once, so there is no performance issue.

Answer 5

String[] allowedFormats = classProperties
                           .getProperty("prop_allowed_extensions", "txt, jpeg")
                           .replaceAll("[ \\.]","")
                           .split(",");

With Java 1.5 or superior, in Array format.

Answer 6

It's much more simple:

String test = classProperties.getProperty("prop_allowed_extensions", "txt, jpeg");
String[] splitString = test.trim().split("\\s*,\\s*");

(needs Java 5)

Answer 7

String test = classProperties.getProperty("prop_allowed_extensions", "txt, jpeg");
String[] splitString = StringUtils.split(test, ',');
for(String s : splitString) {
    s = StringUtils.trim(s);
}

would be slightly more elegant, but Java does not support LINQ like .net where you would be able to avoid the explicit loop altogether.