I have a string and would like to simply replace all of the newlines in it with the string " --linebreak-- ".
Would it be enough to just write:
string = string.replaceAll("\n", " --linebreak-- ");
I'm confused with the regex part of it. Do I need two slashes for the newline? Is this good enough?
Don't use regex!. You only need a plain-text match to replace "\n".
Use replace() to replace a literal string with another:
string = string.replace("\n", " --linebreak-- ");
Note that replace() still replaces all occurrences, as does replaceAll() - the difference is that replaceAll() uses regex to search.
replace() replaces them all. The problem is that replaceAll() is badly named: Both methods replace all occurrences - the only difference between them is that replaceAll() uses regex for finding matches, while replace uses plain text.
string = string.replace("\\n", System.lineSeparator()); Edit: But that is when I'm passing 'new line characters' in from an external source (like from the command line).. so the above code replaces the literal '/n' with an actual 'new line', you might have been trying to do the reverse.Use below regex:
s.replaceAll("\\r?\\n", " --linebreak-- ")
There's only really two newlines for UNIX and Windows OS.
s.replaceAll(/^#.*\\r?\\n/, "") . Example using regex delimiters to remove comments.Since Java 8 regex engine supports \R which represents any line separator (little more info: https://stackoverflow.com/a/31060125/1393766).
So if you have access to Java 8 or above you can use
string = string.replaceAll("\\R", " --linebreak-- ");
No need for 2 backslashes.
String string = "hello \n world" ;
String str = string.replaceAll("\n", " --linebreak-- ");
System.out.println(str);
Output = hello --linebreak-- world
Just adding this for completeness, because the 2 backslash thing is real.
Refer to @dasblinkenlight answer in the following SO question (talking about \t but it applies for \n as well):
java, regular expression, need to escape backslash in regex
"There are two interpretations of escape sequences going on: first by the Java compiler, and then by the regexp engine. When Java compiler sees two slashes, it replaces them with a single slash. When there is t following a slash, Java replaces it with a tab; when there is a t following a double-slash, Java leaves it alone. However, because two slashes have been replaced by a single slash, regexp engine sees \t, and interprets it as a tab."
Looks good. You don't want 2 backslashes.
http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html#sum
for new line there is a property
System.getProperty("line.separator")
Here as for your example,
string.replaceAll("\n", System.getProperty("line.separator"));
In my case I wanted to replace with literal '\n' so I escaped the \ with another \ like so
String input = "a\nb\nc\nd";
/*
a
b
c
d
*/
input = input.replace("\n", "\\n");
System.out.println(input); // a\nb\nc\nd
