Develop Reference

How to convert a ip string xxx.xxx.xxx.xxx:xxxxx to xxx.xxx.xxx.xxx?

I'm getting this ips from my server like:
"/177.127.101.68:53964"
"/201.80.15.100:54263"
"/177.67.38.54:51309"
and i need it to be like just "177.127.101.68", i was going to delete the last 5 string characters but sometimes it comes "/186.213.186.40:4625" so i dont know exactly how to do it... is there any way to do that?

Use the split() and substring() methods of the String class, for one approach:
String ip = "/177.127.101.68:53964";
String whatYouWant = ip.split(":")[0].substring(1);
Please see the Javadocs for split and substring. You'll find yourself using them a lot, in my opinion.

You only need substring:
String ip = "/177.127.101.68:53964";
String result = ip.substring(1, ip.indexOf(':')-1);

Other way around could be something like
String myIP = "/177.127.101.68:53964";
URL url = new URL("http:/" + myIP);// will create URL for http://177.127.101.68:53964
String host = url.getHost(); // will return only 177.127.101.68 part

Using regular expressions to rename a string

In java, I want to rename a String so it always ends with ".mp4"
Suppose we have an encoded link, looking as follows:
String link = www.somehost.com/linkthatIneed.mp4?e=13974etc...
So, how do I rename the link String so it always ends with ".mp4"?
link = www.somehost.com/linkthatIneed.mp4 <--- that's what I need the final String to be.

Just get the string until the .mp4 part using the following regex:
^(.*\.mp4)
and the first captured group is what you want.
Demo: http://regex101.com/r/zQ6tO5

Another way to do this would be to split the string with ".mp4" as a split char and then add it again :)
Something like :
String splitChar = ".mp4";
String link = "www.somehost.com/linkthatIneed.mp4?e=13974etcrezkhjk"
String finalStr = link.split(splitChar)[0] + splitChar;
easy to do ^^
PS: I prefer to pass by regex but it ask for more knowledge about regex ^^

Well you can also do this:
Match the string with the below regex
\?.*
and replace it with empty string.
Demo: http://regex101.com/r/iV1cZ8

Try below code,
private String trimStringAfterOccurance(String link, String occuranceString) {
Integer occuranceIndex = link.indexOf(occuranceString);
String trimmedString = (String) link.subSequence(0, occuranceIndex + occuranceString.length() );
System.out.println(trimmedString);
return trimmedString;
}

More efficient way splitting than this?

Is there a more efficient way of splitting a string than this?
String input = "=example>";
String[] split = input.split("=");
String[] split1 = split[1].split(">");
String result = split1[0];
The result would be "example".

String result = input.replaceAll("[=>]", "");
Very simple regex!
To learn more, go to this link: here

Do you really need regex. You can do:
String result = input.substring(1, input.length()-1);
Otherwise if you really have a case for regex then use character class:
String result = input.replaceAll("[=>]", "");

If you just want to get example out of that do this:
input.substring(1, input.lastIndexOf(">"))

If the string of yours defenitely constant format use substring otherwise go fo regex
result = result.substring(1, result.length() - 1);

You can do it more elegant with RegEx groups:
String sourceString = "=example>";
// When matching, we can "mark" a part of the matched pattern with parentheses...
String patternString = "=(.*?)>";
Pattern p = Pattern.compile(patternString);
Matcher m = p.matcher(sourceString);
m.find();
// ... and access it later
String result = m.group(1);

You can try this regex: ".*?((?:[a-z][a-z]+))"
But it would be better when you use something like this:
String result = input.substring(1, input.length()-1);

try this
String result = input.replace("[\\W]", "")

You can try this too
String input = "=example>";
System.out.println(input.replaceAll("[^\\p{L}\\p{Nd}]", ""));
This will remove all non-words characters

Regex would do the job perfectly, but just to add something new for future solutions you also could use a third party lib such as Guava from Google, it adds a lot of functionalities to your project and the Splitter is really helpful to solve something like you have.

Java replaceall ignore case and special characters

This is just an example code of the thing i try to accomplish.
String s = "hello(1234aA)something";
String replaceString = "(1234aa)";
String s2 = s.replaceAll("(i?)" + replaceString, "something");
The String s is going to be the same but can differ in case, thats why i use (i?) in replaceall.
How can i make regex ignore the special

Use quote(), it seems you've already figured out the ignore case, but you should use (?i), not (i?).
String s = "hello(1234aA)something";
String replaceString = "(?i)" + Pattern.quote("(1234aa)");
String s2 = s.replaceAll(replaceString, "something");
This should work.

Need to Trim Java String

I need help in trimming a string url.
Let's say the String is http://myurl.com/users/232222232/pageid
What i would like returned would be /232222232/pageid
Now the 'myurl.com' can change but the /users/ will always be the same.

I suggest you use substring and indexOf("/users/").
String url = "http://myurl.com/users/232222232/pageid";
String lastPart = url.substring(url.indexOf("/users/") + 6);
System.out.println(lastPart); // prints "/232222232/pageid"
A slightly more sophisticated variant would be to let the URL class parse the url for you:
URL url = new URL("http://myurl.com/users/232222232/pageid");
String lastPart = url.getPath().substring(6);
System.out.println(lastPart); // prints "/232222232/pageid"
And, a third approach, using regular expressions:
String url = "http://myurl.com/users/232222232/pageid";
String lastPart = url.replaceAll(".*/users", "");
System.out.println(lastPart); // prints "/232222232/pageid"

string.replaceAll(".*/users(/.*/.*)", "$1");

String rest = url.substring(url.indexOf("/users/") + 6);

You can use split(String regex,int limit) which will split the string around the pattern in regex at most limit times, so...
String url="http://myurl.com/users/232222232/pageid";
String[] parts=url.split("/users",1);
//parts={"http://myurl.com","/232222232/pageid"}
String rest=parts[1];
//rest="/232222232/pageid"
The limit is there to prevent strings like "http://myurl.com/users/232222232/users/pageid" giving answers like "/232222232".

You can use String.indexOf() and String.substring() in order to achieve this:
String pattern = "/users/";
String url = "http://myurl.com/users/232222232/pageid";
System.out.println(url.substring(url.indexOf(pattern)+pattern.length()-1);