Replace a String between two Strings

Question

Let's say we have something like:

&firstString=someText&endString=OtherText

And I would like to replace "someText" with something else. What is the best way to do this considering the fact that I do not know what someText might be (any string) and all I know is that it will be surrounded with &firstString= and &endString=

Edit: sorry looks like this is not clear enough. I do not know what "someText" might be, the only information I have is that it will be between &firstString= and &endString=

I was thinking about using split multiple times but it sounded ugly ..

What exactly is it that you need to do? And what have you tried so far? — Gareth McCaughan, May 01 '12 at 20:12
I added a clarification to the question, sorry if it wasn't clear enough :) — user220755, May 01 '12 at 20:14

score 26 · Accepted Answer · answered May 01 '12 at 20:20

26

You can use String#replaceAll that has support for regex like this:

String newstr = str.replaceAll("(&firstString=)[^&]*(&endString=)", "$1foo$2");

answered May 01 '12 at 20:20

anubhava

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2

public static String replaceBetween(String theString, String value, String open, String close) { return theString.replaceAll("(" + open + ")[^&]*(" + close + ")", "$1" + value + "$2"); } – markthegrea Sep 07 '18 at 19:20
What would be the time performance as compared to using sed or perl commands to replace the string? – Abhishek Attri Jan 15 '19 at 09:01
1

This is Java question so obviously there is no comparison with Unix tools – anubhava Jan 15 '19 at 10:28

score 5 · Answer 2 · edited Oct 01 '15 at 16:28

The easiest to understand way to do it is to search for the delimiters, and cut out a substring between their positions, like this:

String str = "&firstString=someText&endString=OtherText";
String firstDelim = "&firstString=";
int p1 = str.indexOf(firstDelim);
String lastDelim = "&endString=";
int p2 = str.indexOf(lastDelim, p1);   // look after start delimiter    
String replacement = "quick_brown_fox";
if (p1 >= 0 && p2 > p1) {
    String res = str.substring(0, p1+firstDelim.length())
               + replacement
               + str.substring(p2);
    System.out.println(res);
}

score 3 · Answer 3 · edited Oct 01 '15 at 16:54

3

yourString.replace("someText", "somethingElse");

EDIT based on clarification

String x = "&firstString=someText&endString=OtherText";
int firstPos = x.indexOf("&firstString=") + "&firstString=".length();
int lastPos = x.indexOf("&endString", firstPos);
String y = x.substring(0,firstPos) + "Your new text" + x.substring(lastPos);
System.out.println(y);

Output:

&firstString=Your new text&endString=OtherText

edited Oct 01 '15 at 16:54

Greg Valcourt

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answered May 01 '12 at 20:11

dcp

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I just clarified the question further. I do not know what sometext might be (I only know the strings around it) – user220755 May 01 '12 at 20:14
The title is: "Replace a String between two strings" :) Sorry again if it wasn't clear, my fault :) – user220755 May 01 '12 at 20:16

İsmet Alkan · Answer 4 · 2012-05-01T20:28:18.743

1

As I understood the question, you should do something like this, but I'm not sure I totally got what you asked:

yourString = firstString + replacingString + endString;

If you want the "replaced" string:

replacedString = wholeString.substring(0, wholeString.lastIndexOf(endString) - 1);
replacedString = tempString.substring(firstString.length() + 1);

edited May 01 '12 at 20:28

answered May 01 '12 at 20:19

İsmet Alkan

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score 0 · Answer 5 · edited Sep 22 '16 at 19:54

This solution checks that we're not going of the end of the string and will do it for multiple occurrences.

 int startIndex = text.indexOf(startDelim);
 while (startIndex > -1)
 {
    int endIndex = text.indexOf(endDelim, startIndex);
    String endPart = "";

    if ((endIndex + endDelim.length()) < text.length())
       endPart = text.substring(endIndex + endDelim.length());

    text = text.substring(0, startIndex) + replacementText + endPart;
    startIndex = text.indexOf(startDelim);
 }

score -1 · Answer 6 · answered May 01 '12 at 20:11

-1

just replacing the whole &firstString=someText& since this includes the outer barriers which I assume to be URL related?

answered May 01 '12 at 20:11

Omnaest

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I just clarified the question further. I do not know what sometext might be (I only know the strings around it) – user220755 May 01 '12 at 20:14
@user220755 yeah, then use that regex stuff mentioned by dcp and replace sometext with [^\\&]* – Omnaest May 01 '12 at 20:16
can you explain a little further? – user220755 May 01 '12 at 20:18

Replace a String between two Strings

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