String parsing, replace new line character

Question

I have one issue regarding string parsing.

String str = "jdaskks sms=<hello
hi wini>";

Here u can see, the new line character present in string. I have written a program, which searches for sms= string , then gets substring from < > character. in which i check for new line character and replace it with ' '.

But i have issue, when i get substring . i replace it. but how to change this in original string str, as i can see change in substring not in original string.

Help is appreciated.

str.substring(j,str.indexOf('>',j+1)).replaceAll("\n", "#10");
here j is index of '<'

If i assign this string, i will get the substring with replace char, not original string with replaced new line character

So, you just get the string between `<...>` and replace the newline with a regular space? — Wiktor Stribiżew, Mar 09 '16 at 15:57
Possible duplicate of [Immutability of Strings in Java](http://stackoverflow.com/questions/1552301/immutability-of-strings-in-java) — david, Mar 09 '16 at 16:05
@WiktorStribiżew Yes, but i need to change in original string — Wini, Mar 09 '16 at 16:16

Andy Turner · Accepted Answer · 2016-03-09T16:11:36.357

3

Strings are immutable in Java - operations like replace don't actually update the original string. You have to use the return value of the substring call, e.g.

String updated = str.substring(j,str.indexOf('>',j+1)).replaceAll("\n", "#10");

If you want to replace this in the overall string, you can simply concatenate this back into the string:

int indexOf = str.indexOf('>',j+1);
str = str.substring(0, j)
    + str.substring(j,indexOf).replaceAll("\n", "#10"))
    + str.substring(indexOf);

edited Mar 09 '16 at 16:11

answered Mar 09 '16 at 15:58

Andy Turner

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But, original string will be lost right. as in my example, jdaskks will be lost. i will get substring, not the original string with replaced new line character – Wini Mar 09 '16 at 16:07
what part dont you understand about immutable? – Gregorio Meraz Jr. Mar 09 '16 at 22:22

score 1 · Answer 2 · answered Mar 09 '16 at 16:03

You are able to get the substring but you are not assigning it to a string or using for displaying.Because strings are immutable.

So just assign result to a new string:

String result= str.substring(j,str.indexOf('>',j+1)).replaceAll("\n", "#10");

or use it for displaying.

System.Out.Println(str.substring(j,str.indexOf('>',j+1)).replaceAll("\n", "#10"));

score 0 · Answer 3 · answered Mar 09 '16 at 16:01

0

As you have created a new String object but didn't assign it back to a variable, is the cause of you issue.

answered Mar 09 '16 at 16:01

Rishi

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String parsing, replace new line character

3 Answers3