Develop Reference

What is the efficient way to get a specific substring from a string in Java?

I have a string as follows:
"[error=<null>,EntityID=105378032, Context=<null>]"
and i want to extract the EntityID( in this case 105378032), but i want a generalize solution of doing it.
What is the most efficient way of doing it.
I don't want to traverse the string and get that part.

Did you try regex like .*EntityID=(.*?),.* which mean get the group of characters between EntityID= and the next comma , using replaceAll :
String str = "[error=,EntityID=105378032, Context=]";
System.out.println(str.replaceAll(".*EntityID=(.*?),.*", "$1"));// output 105378032
regex demo

Using Regular expressions seems to be the best way out.
This code works:
String str = "[error=,EntityID=105378032, Context=]";
String[] arr = str.split("EntityID="); //splits it on the part "EntityID="
String[] arr1 = arr[1].split(","); // splits it on the next comma in the 'right' half of your string.
System.out.println(arr1[0]); //prints the 'left' half before the comma.
Ideone link here.
Hope this helps!

You can use this method it's work like a charm
public static String getSubString(String mainString, String lastString, String startString) {
String endString = "";
int endIndex = mainString.indexOf(lastString);
int startIndex = mainString.indexOf(startString);
endString = mainString.substring(startIndex, endIndex);
return endString;
}
Result:
String resultStr = getSubString(yourFullString,",Context","EntityID=");
Happy codding.

How to Remove string after second last occurrence of special character?

In my application I am trying to make breadcrumbs using StringBuilder
Suppose this is the string :
String1>String2>String3>String4>String5>
Now I want to remove String5> and I want string like this:
String1>String2>String3>String4>
How can I do this?
Please help!!

you can use regex \\w+>$
\\w+ mean match [a-zA-Z0-9_]
>$ match > character where $ mean at the end
Regex Demo Link
String s = "String1>String2>String3>String4>String5>";
String s2 = s.replaceAll("\\w+>$","");
System.out.println(s2);
Output :
String1>String2>String3>String4>
Note : To avoid _ use
String s2 = s.replaceAll("[a-zA-Z\\d]+>$","");
Just in case if you have data with some special characters like
String s = "String1>Stri$#$ng2>String3>Stri#$$#ng4>St$#:/|ring5>";
then above solution won't work so you can use
String s2 = s.replaceAll("[^>]+>$","");
// s2 will be = String1>Stri$#$ng2>String3>Stri#$$#ng4>
Regex Demo Link
[^>]+ : ^ inside [] works as negation mean match everything except > character

Split string by > and then apply for loop on the array. match string by position. if match then delete otherwise add to new stringBuilder.

You can use combination of lastIndexOf and substring().
Example:
String oldValue = "String1>String2>String3>String4>String5>";
int lastIndex = oldValue.lastIndexOf('>', oldValue.length() - 2);
String newValue = oldValue.substring(0, lastIndex + 1);

Replace value in a regex

I have the next String in java:
|ABC|50200|100|50200|200|PRUEBA|ABC|20150220184512|
So I need to replace the value |50200| (second one) with other value according to some decisions,but only need to replace the second one, how can I do, since replace or replaceAll don't work in this case. I was trying with some regex and appendReplacement but it did not work,also I need it to be as quick as possible, code below:
String event = "|ABC|50200|100|50200|200|PRUEBA|ABC|20150220184512|";
Pattern p = Pattern.compile("^\|(\w*)\|(\d+)\|(\d+(\.\d{1,})*)\|(\d+(\.\d{1,})*)\|(\d+(\.\d{1,})*)\|\w+\|\w+\|\d{14}\|$");
Matcher mat = p.matcher(event);
StringBuffer aux = new StringBuffer();
mat.appendReplacement(aux, mat.group(5));
String newString = aux.toString();
But the value of newString is 50200, so basically I want to replace it with 12345, so the String would look like this |ABC|50200|100|12345|200|PRUEBA|ABC|20150220184512|
Thanks in advance for your help
The thing is I have to use the regex to check the format of the String before doing the replace, because there could be other String with different formats

You can use indexOf to find the second position, then substring around the value you want to replace.
For example
public static void main(String[] args) {
String s = "|ABC|50200|100|50200|200|PRUEBA|ABC|20150220184512|";
String find = "50200";
String replace = "12345";
int firstOccur = s.indexOf(find);
int secondOccur = s.indexOf(find, firstOccur+find.length());
StringBuilder sb = new StringBuilder(s.substring(0, secondOccur));
sb.append(replace);
sb.append(s.substring(secondOccur+find.length()));
System.out.println(sb.toString());
// |ABC|50200|100|12345|200|PRUEBA|ABC|20150220184512|
}

Since question has been tagged as regex and non-regex solution is possible but a bit longish here is a simple one line regex solution:
String data = "|ABC|50200|100|50200|200|PRUEBA|ABC|20150220184512|";
String srch = "|50200|";
String repl = "|12345|";
String rdata = data.replaceFirst("^(.*?(\\|50200\\|).*?)\\2", "$1|12345|");
//=> |ABC|50200|100|12345|200|PRUEBA|ABC|20150220184512|
Regex ^(.*?(\|50200\|).*?)\2 finds 2nd instance of |50200| and captures everything before 2nd instance into captured group #1. We use backreference $1 in replacement to put that captured text back.
RegEx Demo

Remove trailing substring from String in Java

I am looking to remove parts of a string if it ends in a certain string.
An example would be to take this string: "am.sunrise.ios#2x.png"
And remove the #2x.png so it looks like: "am.sunrise.ios"
How would I go about checking to see if the end of a string contains "#2x.png" and remove it?

You could check the lastIndexOf, and if it exists in the string, use substring to remove it:
String str = "am.sunrise.ios#2x.png";
String search = "#2x.png";
int index = str.lastIndexOf(search);
if (index > 0) {
str = str.substring(0, index);
}

Assuming you have a string initialized as String file = "am.sunrise.ios#2x.png";.
if(file.endsWith("#2x.png"))
file = file.substring(0, file.lastIndexOf("#2x.png"));
The endsWith(String) method returns a boolean determining if the string has a certain suffix. Depending on that you can replace the string with a substring of itself starting with the first character and ending before the index of the character that you are trying to remove.

private static String removeSuffixIfExists(String key, String suffix) {
return key.endswith(suffix)
? key.substring(0, key.length() - suffix.length())
: key;
}
}
String suffix = "#2x.png";
String key = "am.sunrise.ios#2x.png";
String output = removeSuffixIfExists(key, suffix);

public static void main(String [] args){
String word = "am.sunrise.ios#2x.png";
word = word.replace("#2x.png", "");
System.out.println(word);
}

If you want to generally remove entire content of string from # till end you can use
yourString = yourString.replaceAll("#.*","");
where #.* is regex (regular expression) representing substring starting with # and having any character after it (represented by .) zero or more times (represented by *).
In case there will be no #xxx part your string will be unchanged.
If you want to change only this particular substring #2x.png (and not substirng like #3x.png) while making sure that it is placed at end of your string you can use
yourString = yourString.replaceAll("#2x\\.png$","");
where
$ represents end of string
\\. represents . literal (we need to escape it since like shown earlier . is metacharacter representing any character)

Since I was trying to do this on an ArrayList of items similarly styled I ended up using the following code:
for (int image = 0; image < IBImages.size(); image++) {
IBImages.set(image, IBImages.get(image).split("~")[0].split("#")[0].split(".png")[0]);
}
If I have a list of images with the names
[am.sunrise.ios.png, am.sunrise.ios#2x.png, am.sunrise.ios#3x.png, am.sunrise.ios~ipad.png, am.sunrise.ios~ipad#2x.png]
This allows me to split the string into 2 parts.
For example, "am.sunrise.ios~ipad.png" will be split into "am.sunrise.ios" and "~ipad.png" if I split on "~". I can just get the first part back by referencing [0]. Therefore I get what I'm looking for in one line of code.
Note that image is "am.sunrise.ios~ipad.png"

You could use String.split():
public static void main(String [] args){
String word = "am.sunrise.ios#2x.png";
String[] parts = word.split("#");
if (parts.length == 2) {
System.out.println("looks like user#host...");
System.out.println("User: " + parts[0]);
System.out.println("Host: " + parts[1]);
}
}
Then you haven an array of Strings, where the first element contains the part before "#" and the second element the part after the "#".

Combining the answers 1 and 2:
String str = "am.sunrise.ios#2x.png";
String search = "#2x.png";
if (str.endsWith(search)) {
str = str.substring(0, str.lastIndexOf(search));
}

Getting the last part of the string

I have a string :
"id=40114662&mode=Edit&reminderId=44195234"
All i want from this string is the final number 44195234. I can't use :
String reminderIdFin = reminderId.substring(reminderId.lastIndexOf("reminderId=")+1);
as i cant have the = sign as the point it splits the string. Is there any other way ?

Try String.split(),
reminderIdFin.split("=")[3];

You can use indexOf() method to get where this part starts:
int index = reminderIdFin.indexOf("Id=") + 3;
the plus 3 will make it so that it jumps over these characters. Then you can use substring to pull out your wanted string:
String newString = reminderIdFin.substring(index);

Remove everything else and you'll be left with your target content:
String reminderIdFin = reminderId.replaceAll(".*=", "");
The regex matches everything up to the last = (the .* is "greedy").