I have a string like this:
something:POST:/some/path
Now I want to take the POST alone from the string. I did this by using this regex
:([a-zA-Z]+):
But this gives me a value along with colons. ie I get this:
:POST:
but I need this
POST
My code to match the same and replace it is as follows:
String ss = "something:POST:/some/path/";
Pattern pattern = Pattern.compile(":([a-zA-Z]+):");
Matcher matcher = pattern.matcher(ss);
if (matcher.find()) {
System.out.println(matcher.group());
ss = ss.replaceFirst(":([a-zA-Z]+):", "*");
}
System.out.println(ss);
EDIT:
I've decided to use the lookahead/lookbehind regex since I did not want to use replace with colons such as :*:. This is my final solution.
String s = "something:POST:/some/path/";
String regex = "(?<=:)[a-zA-Z]+(?=:)";
Matcher matcher = Pattern.compile(regex).matcher(s);
if (matcher.find()) {
s = s.replaceFirst(matcher.group(), "*");
System.out.println("replaced: " + s);
}
else {
System.out.println("not replaced: " + s);
}
There are two approaches:
Keep your Java code, and use lookahead/lookbehind (?<=:)[a-zA-Z]+(?=:), or
Change your Java code to replace the result with ":*:"
Note: You may want to define a String constant for your regex, since you use it in different calls.
As pointed out, the reqex captured group can be used to replace.
The following code did it:
String ss = "something:POST:/some/path/";
Pattern pattern = Pattern.compile(":([a-zA-Z]+):");
Matcher matcher = pattern.matcher(ss);
if (matcher.find()) {
ss = ss.replaceFirst(matcher.group(1), "*");
}
System.out.println(ss);
UPDATE
Looking at your update, you just need ReplaceFirst only:
String result = s.replaceFirst(":[a-zA-Z]+:", ":*:");
See the Java demo
When you use (?<=:)[a-zA-Z]+(?=:), the regex engine checks each location inside the string for a * before it, and once found, tries to match 1+ ASCII letters and then assert that there is a : after them. With :[A-Za-z]+:, the checking only starts after a regex engine found : character. Then, after matching :POST:, the replacement pattern replaces the whole match. It is totlally OK to hardcode colons in the replacement pattern since they are hardcoded in the regex pattern.
Original answer
You just need to access Group 1:
if (matcher.find()) {
System.out.println(matcher.group(1));
}
See Java demo
Your :([a-zA-Z]+): regex contains a capturing group (see (....) subpattern). These groups are numbered automatically: the first one has an index of 1, the second has the index of 2, etc.
To replace it, use Matcher#appendReplacement():
String s = "something:POST:/some/path/";
StringBuffer result = new StringBuffer();
Matcher m = Pattern.compile(":([a-zA-Z]+):").matcher(s);
while (m.find()) {
m.appendReplacement(result, ":*:");
}
m.appendTail(result);
System.out.println(result.toString());
See another demo
This is your solution:
regex = (:)([a-zA-Z]+)(:)
And code is:
String ss = "something:POST:/some/path/";
ss = ss.replaceFirst("(:)([a-zA-Z]+)(:)", "$1*$3");
ss now contains:
something:*:/some/path/
Which I believe is what you are looking for...
Related
I'm trying to replace a url string to lowercase but wanted to keep the certain pattern string as it is.
eg: for input like:
http://BLABLABLA?qUERY=sth¯o1=${MACRO_STR1}¯o2=${macro_str2}
The expected output would be lowercased url but the multiple macros are original:
http://blablabla?query=sth¯o1=${MACRO_STR1}¯o2=${macro_str2}
I was trying to capture the strings using regex but didn't figure out a proper way to do the replacement. Also it seemed using replaceAll() doesn't do the job. Any hint please?
It looks like you want to change any uppercase character which is not inside ${...} to its lowercase form.
With construct
Matcher matcher = ...
StringBuffer buffer = new StringBuffer();
while (matcher.find()){
String matchedPart = ...
...
matcher.appendReplacement(buffer, replacement);
}
matcher.appendTail(buffer);
String result = buffer.toString();
or since Java 9 we can use Matcher#replaceAll​(Function<MatchResult,String> replacer) and rewrite it like
String replaced = matcher.replaceAll(m -> {
String matchedPart = m.group();
...
return replacement;
});
you can dynamically build replacement based on matchedPart.
So you can let your regex first try to match ${...} and later (when ${..} will not be matched because regex cursor will not be placed before it) let it match [A-Z]. While iterating over matches you can decide based on match result (like its length or if it starts with $) if you want to use use as replacement its lowercase form or original form.
BTW regex engine allows us to place in replacement part $x (where x is group id) or ${name} (where name is named group) so we could reuse those parts of match. But if we want to place ${..} as literal in replacement we need to escape \$. To not do it manually we can use Matcher.quoteReplacement.
Demo:
String yourUrlString = "http://BLABLABLA?qUERY=sth¯o1=${MACRO_STR1}¯o2=${macro_str2}";
Pattern p = Pattern.compile("\\$\\{[^}]+\\}|[A-Z]");
Matcher m = p.matcher(yourUrlString);
StringBuffer sb = new StringBuffer();
while(m.find()){
String match = m.group();
if (match.length() == 1){
m.appendReplacement(sb, match.toLowerCase());
} else {
m.appendReplacement(sb, Matcher.quoteReplacement(match));
}
}
m.appendTail(sb);
String replaced = sb.toString();
System.out.println(replaced);
or in Java 9
String replaced = Pattern.compile("\\$\\{[^}]+\\}|[A-Z]")
.matcher(yourUrlString)
.replaceAll(m -> {
String match = m.group();
if (match.length() == 1)
return match.toLowerCase();
else
return Matcher.quoteReplacement(match);
});
System.out.println(replaced);
Output: http://blablabla?query=sth¯o1=${MACRO_STR1}¯o2=${macro_str2}
This regex will match all the characters before the first ¯o, and put everything between http:// and the first ¯o in its own group so you can modify it.
http://(.*?)¯o
Tested here
UPDATE: If you don't want to use groups, this regex will match only the characters between http:// and the first ¯o
(?<=http://)(.*?)(?=¯o)
Tested here
I want to check the text to see if it starts with what or who and and is a question type, so for that I wrote the following code:
private static void startWithQOrIf(String commentstr){
String urlPattern = "(|who|what).*\\?.*$";
Pattern p = Pattern.compile(urlPattern,Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(commentstr);
if (m.find()) {
System.out.println("yes");
}
}
everything works good but for example when I try:
whooooooooo is the follower?
will match as well but should not because I am looking for who not whooooooooo
Any idea?
You can ensure a whole word using a word boundary \b:
(|who|what)\\b.*\\?.*$
^^
If the words in the alternation group are supposed to appear at the start of the string, you can just use matches and remove $ anchor:
String urlPattern = "(|who|what)\\b.*\\?.*";
Pattern p = Pattern.compile(urlPattern,Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(commentstr);
if (m.matches()) { // < - Here, matches is used
System.out.println("yes");
}
Note that (|who|what) matches either an empty string, or who, or what. If you do not plan to allow empty string, use just (who|what).
You must use word boundaries.
String urlPattern = "\\b(who|what)\\b.*\\?.*$";
String output = "";
pattern = Pattern.compile(">Part\s.");
matcher = pattern.matcher(docToProcess);
while (matcher.find()) {
match = matcher.group();
}
I'm trying to use the above code to find the pattern >Part\s. inside docToProcess (Which is a string of a large xml document) and then what I want to do is replace the content that matches the pattern with <ref></ref>
Any ideas how I can make the output variable equal to docToProcess except with the replacements as indicated above?
EDIT: I need to use the matcher somehow when replacing. I can't just use replaceAll()
You can use String#replaceAll method. It takes a Regex as first parameter: -
String output = docToProcess.replaceAll(">Part\\s\\.", "<ref></ref>");
Note that, dot (.) is a special meta-character in regex, which matches everything, and not just a dot(.). So, you need to escape it, unless you really wanted to match any character after >Part\\s. And you need to add 2 backslashes to escape in Java.
If you want to use Matcher class, the you can use Matcher.appendReplacement method: -
String docToProcess = "XYZ>Part .asdf";
Pattern p = Pattern.compile(">Part\\s\\.");
Matcher m = p.matcher(docToProcess);
StringBuffer sb = new StringBuffer();
while (m.find()) {
m.appendReplacement(sb, "<ref></ref>");
}
m.appendTail(sb);
System.out.println(sb.toString());
OUTPUT : -
"XYZ<ref></ref>asdf"
This is what you need:
String docToProcess = "... your xml here ...";
Pattern pattern = Pattern.compile(">Part\\s.");
Matcher matcher = pattern.matcher(docToProcess);
StringBuffer output = new StringBuffer();
while (matcher.find()) matcher.appendReplacement(output, "<ref></ref>");
matcher.appendTail(output);
Unfortunately, you can't use the StringBuilder due to historical constraints on the Java API.
docToProcess.replaceAll(">Part\\s[.]", "<ref></ref>");
String output = docToProcess.replaceAll(">Part\\s\\.", "<ref></ref>");
i am new to regular expressions in Java. I like to extract a string by using regular expressions.
This is my String: "Hello,World"
I like to extract the text after ",". The result would be "World". I tried this:
final Pattern pattern = Pattern.compile(",(.+?)");
final Matcher matcher = pattern.matcher("Hello,World");
matcher.find();
But what would be the next step?
You don't need Regex for this. You can simply split on comma and get the 2nd element from the array: -
System.out.println("Hello,World".split(",")[1]);
OUTPUT: -
World
But if you want to use Regex, you need to remove ? from your Regex.
? after + is used for Reluctant matching. It will only match W and stop there.
You don't need that here. You need to match until it can match.
So use greedy matching instead.
Here's the code with modified Regex: -
final Pattern pattern = Pattern.compile(",(.+)");
final Matcher matcher = pattern.matcher("Hello,World");
if (matcher.find()) {
System.out.println(matcher.group(1));
}
OUTPUT: -
World
Extending what you have, you need to remove the ? sign from your pattern to use the greedy matching and then process the matched group:
final Pattern pattern = Pattern.compile(",(.+)"); // removed your '?'
final Matcher matcher = pattern.matcher("Hello,World");
while (matcher.find()) {
String result = matcher.group(1);
// work with result
}
Other answers suggest different approaches to your problem and might offer better solution for what you need.
System.out.println( "Hello,World".replaceAll(".*,(.*)","$1") ); // output is "World"
You are using a reluctant expression and will only select a single character W, whereas you can use a greedy one and print your matched group content:
final Pattern pattern = Pattern.compile(",(.+)");
final Matcher matcher = pattern.matcher("Hello,World");
if (matcher.find()) {
System.out.println(matcher.group(1));
}
Output:
World
See Regex Pattern doc
I am trying to match a regex pattern in Java, and I have two questions:
Inside the pattern I'm looking for there is a known beginning and then an unknown string that I want to get up until the first occurrence of an &.
there are multiple occurrences of these patterns in the line and I would like to get each occurrence separately.
For example I have this input line:
1234567 100,110,116,129,139,140,144,146 http://www.gold.com/shc/s/c_10153_12605_Computers+%26+Electronics_Televisions?filter=Screen+Refresh+Rate%7C120HZ%5EScreen+Size%7C37+in.+to+42+in.&sName=View+All&viewItems=25&subCatView=true ISx20070515x00001a http://www.gold.com/shc/s/c_10153_12605_Computers+%26+Electronics_Televisions?filter=Screen+Refresh+Rate%7C120HZ&sName=View+All&subCatView=true 0 2819357575609397706
And I am interested in these strings:
Screen+Refresh+Rate%7C120HZ%5EScreen+Size%7C37+in.+to+42+in.
Screen+Refresh+Rate%7C120HZ
Assuming the known beginning is filter=**, the regular expression pattern (?:filter=\\*\\*)(.*?)(?:&) should get you what you need. Use Matcher.find() to get all occurrences of the pattern in a given string. Using the test string you provided, the following:
final Pattern p = Pattern.compile("(?:filter=\\*\\*)(.*?)(?:&)");
final Matcher m = p.matcher(testString);
int cnt = 0;
while (m.find()) {
System.out.println(++cnt + ": G1: " + m.group(1));
}
Will output:
1: G1: Screen+Refresh+Rate%7C120HZ%5EScreen+Size%7C37+in.+to+42+in.
2: G1: Screen+Refresh+Rate%7C120HZ**
If i know that I might need other query parameters in the future, I think it'll be more prudent to decode and parse the URL.
String url = URLDecoder.decode("http://www.gold.com/shc/s/c_10153_12605_" +
"Computers+%26+Electronics_Televisions?filter=Screen+Refresh+Rate" +
"%7C120HZ%5EScreen+Size%7C37+in.+to+42+in.&sName=View+All&viewItems=25&subCatView=true"
,"utf-8");
Pattern amp = Pattern.compile("&");
Pattern eq = Pattern.compile("=");
Map<String, String> params = new HashMap<String, String>();
String queryString = url.substring(url.indexOf('?') + 1);
for(String param : amp.split(queryString)) {
String[] pair = eq.split(param);
params.put(pair[0], pair[1]);
}
for(Entry<String, String> param : params.entrySet()) {
System.out.format("%s = %s\n", param.getKey(), param.getValue());
}
Output
subCatView = true
viewItems = 25
sName = View All
filter = Screen Refresh Rate|120HZ^Screen Size|37 in. to 42 in.
in your example, there is sometimes a "**" at the end before the "&". but basically, (assuming "filter=" is the start pattern you are looking for) you want something like:
"filter=([^&]+)&"
Using the regular expression (?<=filter=\*{0,2})[^&]*[^&*]+ in java:
Pattern p = Pattern.compile("(?<=filter=\\*{0,2})[^&]*[^&*]+");
String s = "1234567 100,110,116,129,139,140,144,146 http://www.gold.com/shc/s/c_10153_12605_Computers+%26+Electronics_Televisions?filter=**Screen+Refresh+Rate%7C120HZ%5EScreen+Size%7C37+in.+to+42+in.&sName=View+All**&viewItems=25&subCatView=true ISx20070515x00001a http://www.gold.com/shc/s/c_10153_12605_Computers+%26+Electronics_Televisions?filter=**Screen+Refresh+Rate%7C120HZ**&sName=View+All&subCatView=true 0 2819357575609397706";
Matcher m = p.matcher(s);
while (m.find()) {
System.out.println(m.group());
}
EDIT:
Added [^&*]+ to the end of the regex to prevent the ** from being included in the second match.
EDIT2:
Changed regular expression to use lookbehind.
The regex you're looking for is
Screen\+Refresh\+Rate[^&]*
You could use Matcher.find() to find all matches.
are you looking for a string that follows with "filter=" and ignores the first "*" and is end with the first "&".
your can try the following:
String str = "1234567 100,110,116,129,139,140,144,146 http://www.gold.com/shc/s/c_10153_12605_Computers+%26+Electronics_Televisions?filter=**Screen+Refresh+Rate%7C120HZ%5EScreen+Size%7C37+in.+to+42+in.&sName=View+All**&viewItems=25&subCatView=true ISx20070515x00001a http://www.gold.com/shc/s/c_10153_12605_Computers+%26+Electronics_Televisions?filter=**Screen+Refresh+Rate%7C120HZ**&sName=View+All&subCatView=true 0 2819357575609397706";
Pattern p = Pattern.compile("filter=(?:\\**)([^&]+?)(?:\\**)&");
Matcher matcher = p.matcher(str);
while(matcher.find()){
System.out.println(matcher.group(1));
}