Develop Reference

N-th indexOf in String?

I need to extract a sub-string of a URL.
URLs
/service1/api/v1.0/foo -> foo
/service1/api/v1.0/foo/{fooId} -> foo/{fooId}
/service1/api/v1.0/foo/{fooId}/boo -> foo/{fooId}/boo
And some of those URLs may have request parameters.
Code
String str = request.getRequestURI();
str = str.substring(str.indexOf("/") + 1);
str = str.substring(str.indexOf("/") + 1);
str = str.substring(str.indexOf("/") + 1);
str = str.substring(str.indexOf("/") + 1, str.indexOf("?"));
Is there a better way to extract the sub-string instead of recurrent usage of indexOf method?

There are many alternative ways:
Use Java-Stream API on splitted String with \ delimiter:
String str = "/service1/api/v1.0/foo/{fooId}/boo";
String[] split = str.split("\\/");
String url = Arrays.stream(split).skip(4).collect(Collectors.joining("/"));
System.out.println(url);
With the elimination of the parameter, the Stream would be like:
String url = Arrays.stream(split)
.skip(4)
.map(i -> i.replaceAll("\\?.+", ""))
.collect(Collectors.joining("/"));
This is also where Regex takes its place! Use the classes Pattern and Matcher.
String str = "/service1/api/v1.0/foo/{fooId}/boo";
Pattern pattern = Pattern.compile("\\/.*?\\/api\\/v\\d+\\.\\d+\\/(.+)");
Matcher matcher = pattern.matcher(str);
while (matcher.find()) {
System.out.println(matcher.group(1));
}
If you rely on the indexOf(..) usage, you might want to use the while-loop.
String str = "/service1/api/v1.0/foo/{fooId}/boo?parameter=value";
String string = str;
while(!string.startsWith("v1.0")) {
string = string.substring(string.indexOf("/") + 1);
}
System.out.println(string.substring(string.indexOf("/") + 1, string.indexOf("?")));
Other answers include a way that if the prefix is not mutable, you might want to use only one call of idndexOf(..) method (#JB Nizet):
string.substring("/service1/api/v1.0/".length(), string.indexOf("?"));
All these solutions are based on your input and fact, the pattern is known, or at least the number of the previous section delimited with \ or the version v1.0 as a checkpoint - the best solution might not appear here since there are unlimited combinations of the URL. You have to know all the possible combinations of input URL to find the best way to handle it.

Path is quite useful for that :
public static void main(String[] args) {
Path root = Paths.get("/service1/api/v1.0/foo");
Path relativize = root.relativize(Paths.get("/service1/api/v1.0/foo/{fooId}/boo"));
System.out.println(relativize);
}
Output :
{fooId}/boo

How about this:
String s = "/service1/api/v1.0/foo/{fooId}/boo";
String[] sArray = s.split("/");
StringBuilder sb = new StringBuilder();
for (int i = 4; i < sArray.length; i++) {
sb.append(sArray[i]).append("/");
}
sb.deleteCharAt(sb.length() - 1);
System.out.println(sb.toString());
Output:
foo/{fooId}/boo
If the url prefix is always /service1/api/v1.0/, you just need to do s.substring("/service1/api/v1.0/".length()).

There are a few good options here.
1) If you know "foo" will always be the 4th token, then you have the right idea already. The only issue with your way is that you have the information you need to be efficient, but you aren't using it. Instead of copying the String multiple times and looping anew from the beginning of the new String, you could just continue from where you left off, 4 times, to find the starting point of what you want.
String str = "/service1/api/v1.0/foo/{fooId}/boo";
// start at the beginning
int start = 0;
// get the 4th index of '/' in the string
for (int i = 0; i != 4; i++) {
// get the next index of '/' after the index 'start'
start = str.indexOf('/',start);
// increase the pointer to the next character after this slash
start++;
}
// get the substring
str = str.substring(start);
This will be far, far more efficient than any regex pattern.
2) Regex: (java.util.regex.*). This will work if you what you want is always preceded by "service1/api/v1.0/". There may be other directories before it, e.g. "one/two/three/service1/api/v1.0/".
// \Q \E will automatically escape any special chars in the path
// (.+) will capture the matched text at that position
// $ marks the end of the string (technically it matches just before '\n')
Pattern pattern = Pattern.compile("/service1/api/v1\\.0/(.+)$");
// get a matcher for it
Matcher matcher = pattern.matcher(str);
// if there is a match
if (matcher.find()) {
// get the captured text
str = matcher.group(1);
}
If your path can vary some, you can use regex to account for it. e.g.: service/api/v3/foo/{bar}/baz/" (note varying number formats and trailing '/') could be matched as well by changing the regex to "/service\\d*/api/v\\d+(?:\\.\\d+)?/(.+)(?:/|$)"

Load CSV and split attributes

I'm trying to load a csv file and split 'timespan' into 'begin' and 'end'. If the timespan consists of one date 'begin' and 'end' are the same.
timespan,someOtherField, ...
27.03.2017 - 31.03.2017,someOtherValue, ...
31.03.2017,someOtherValue, ...
Result:
begin,end,someOtherField
27.03.2017,31.03.2017,someOtherValue, ...
31.03.2017,31.03.2017,someOtherValue, ...
At the moment I'm loading the file line by line using OpenCSV. This works pretty good but i don't know how to split one attribute. Propably I have to parse the CSV into an array?

For any line l you can use StringTokenizer to get the tokens separated by ,:
StringTokenizer tokens = new StringTokenizer(l, ",")
The first token represents timespan, so:
String timespan = tokens.nextToken()
Then you can split timespan based on " - ", so:
String[] startEnd = timespan.split(" - ");
Finally, you have to compute the size of the startEnd, if startEnd.length == 1, then you absolutely know that start begin and end coincides, so startEnd[0],startEnd[0]
otherwise the result would look like the following startEnd[0],startEnd[1]
I hope this could help you solve the problem.

Thanks for your answer! I parsed the csv into an extra class and created an object for each record. The code below shows the splitting of the timespan. I will now rebuild a new csv file from all objects.
// Load CSV as Booking objects
ArrayList<Booking> bookings = Utils.readCSV(csvClean);
for (int i = 0; i < bookings.size(); i++) {
String timespan = bookings.get(i).getTimespan();
String begin = "";
String end = "";
if (timespan.contains(" - ")) {
// Split timespan and set values
String[] parts = timespan.split(" - ");
begin = parts[0].trim();
end = parts[1].trim();
bookings.get(i).setBegin(begin);
bookings.get(i).setEnd(end);
} else {
bookings.get(i).setBegin(timespan.trim());
bookings.get(i).setEnd(timespan.trim());
} // end if else
} // end for

Regex split not working

I want split my string using regex.
String Str = " Dřevo5068Hlína5064Železo5064Obilí4895";
String reg = "(\\D+)(\\d+)(\\D+)(\\d+)(\\D+)(\\d+)(\\D+)(\\d+)";
if (Str.matches(reg)) {
String[] l = Str.split(reg);
System.out.println(Arrays.toString(l));
}
But, output is []. Where is problem?
Edit: I want split to:
Dřevo
5068
Hlína
5064
Železo
5064
Obilí
4895
Then I want get numbers from this String.

if your engine permits look-around, split using this pattern
(?<=\D)(?=\d)|(?<=\d)(?=\D)
Demo

Parsing String and Int in java

Im using java and I have a String that I would like to parse which contains the following
Logging v0.12.4
and would like to split it into a String containing
Logging
and an integer array containing
0.12.4
where
array[i][0] = 0
and
array[i][1] = 12
and so on. I have been stuck on this for a while now.

split your string on space to get Logging and v0.12.4
remove (substring) v from v0.12.4
split 0.12.4 on dot (use split("\\.") since dot is special in regex)
you can also parse each "0" "12" "4" to integer (Integer.parseInt can be helpful).

You can use a regex or just normal String splitting
String myString = "Logging v0.12.4";
String[] parts = myString.split(" v");
// now parts[0] will be "Logging" and
// parts[1] will be "0.12.4";
Then do the same for the version part:
String[] versionParts = parts[1].split("\\.");
// versionParts[0] will be "0"
// versionParts[1] will be "12"
// versionParts[2] will be "4"
You can "convert" these to integers by using Integer.parseInt(...)

Here ya go buddy, because I'm feeling generous today:
String string = "Logging v0.12.4";
Matcher matcher = Pattern.compile("(.+?)\\s+v(.*)").matcher(string);
if (matcher.matches()) {
String name = matcher.group(1);
int[] versions = Arrays.stream(matcher.group(2).split("\\.")).mapToInt(Integer::parseInt).toArray();
}

Extract text from string Java

With this string "ADACADABRA". how to extract "CADA" From string "ADACADABRA" in java.
and also how to extract the id between "/" and "?" from the link below.
http://www.youtube-nocookie.com/embed/zaaU9lJ34c5?rel=0
output should be: zaaU9lJ34c5
but should use "/" and "?" in the process.

and also how to extract the id between "/" and "?" from the link below.
http://www.youtube-nocookie.com/embed/zaaU9lJ34c5?rel=0
output should be: zaaU9lJ34c5
Should be :
String url = "http://www.youtube-nocookie.com/embed/zaaU9lJ34c5?rel=0";
String str = url.substring(url.lastIndexOf("/") + 1, url.indexOf("?"));

String s = "ADACADABRA";
String s2 = s.substring(3,7);
Here 3 specifies the beginning index, and 7 specifies the stopping point.
The string returned contains all the characters from the beginning index, up to, but not including, the ending index.

I'm not entirely sure what you mean by extract, so I've provided the code to remove it from the String, I'm not certain if this is what you want.
public static void main (String args[]){
String string = "ADACADABRA";
string = string.replace("CADA", "");
System.out.println(string);
}

This is untested but something like this may help for the youtube part:
String youtubeUrl = "http://www.youtube-nocookie.com/embed/zaaU9lJ34c5?rel=0";
String[] urlParts = youtubeUrl.split("/");
String videoId = urlParts[urlParts.length - 1];
videoId = videoId.substring(0, videoId.indexOf("?"));
Extracting CADA from the string makes no sense. You will need to specify how you have determined that CADA is the string to extract.
E.g. is it because it is the middle 4 characters? Is it because you are stripping off 3 characters each side? Are you just looking for the String "CADA"? Is it characters 3,7 of the String? Is it the first 4 of the last 7 characters of a String? Is it because it contains 2 vowels and 2 consanants? I could go on..

String regex = "CADA";
Pattern p = Pattern.compile(regex, Pattern.MULTILINE);
Matcher m = p.matcher(originalText);
while (m.find()) {
String outputThis = m.group(1);
}
Use this tool http://www.regexplanet.com/advanced/java/index.html

Probably, you don't take in account the fact of java.lang.String immutability. That's why you need to assign the result of substringing to a new variable.