We Keep Coding

Java split with special characters

I have below code that doing a split for string using <div>\\$\\$PZ\\$\\$</div> and it's not working using the special characters.
public class HelloWorld{
public class HelloWorld{
public static void main(String []args){
String str = "test<div>\\$\\$PZ\\$\\$</div>test";
String[] arrOfStr = str.split("<div>\\$\\$PZ\\$\\$</div>", 2);
for (String a : arrOfStr)
System.out.println(a);
}
}
the output os test<div>\$\$PZ\$\$</div>test
it works when I remove the special characters
Can you please help.

As you already know, the parameter to split(...) is a regular expression, so some characters have special meaning. If you want the parameter to be treated literally, i.e. not as a regex, call the Pattern.quote(String s) method.
Example
String str = "test<div>\\$\\$PZ\\$\\$</div>test";
String[] arrOfStr = str.split(Pattern.quote("<div>\\$\\$PZ\\$\\$</div>"), 2);
for (String a : arrOfStr)
System.out.println(a);
Output
test
test
The quote() method simply surrounds the literal text with the regex \Q...\E quotation pattern1, e.g. your <div>\$\$PZ\$\$</div> text becomes:
\Q<div>\$\$PZ\$\$</div>\E
For fixed text you could just do that yourself, i.e. the following 3 versions all create the same regex to split on:
str.split(Pattern.quote("<div>\\$\\$PZ\\$\\$</div>"), 2)
str.split("\\Q<div>\\$\\$PZ\\$\\$</div>\\E", 2)
str.split("<div>\\\\\\$\\\\\\$PZ\\\\\\$\\\\\\$</div>", 2)
To me, the 3rd one, using \ to escape, is the least readable/desirable version.
If there is a lot of special characters to escape, using \Q...\E is easier than \-escaping all the special characters separately, but very few people use it, so it's fairly unknown to most.
The quote() method is especially useful when you need to treat dynamic text literally, e.g. when the text to split on is configurable by the user.
1) quote() will correctly handle literal text containing \E.

This:
String str = "test<div>\\$\\$PZ\\$\\$</div>test";
String[] arrOfStr = str.split("<div>\\\\\\$\\\\\\$PZ\\\\\\$\\\\\\$</div>", 2);
for (String a : arrOfStr) {
System.out.println(a);
}
prints:
test
test
EDIT: Why do we need all those backslashes? It's because of how we need to handle String literals representing regex expressions. This page describes the reason with examples. The essence is this:
For a backslash \...
...the pattern to match that would be \\... (to escape the escape)
... but the string literal to create that pattern would have to have one backslash to escape each of the two backslashes: \\\\.
Add to that the original need to also escape the $, that gives us our 6 backslashes in the string representation.

Split string against some characters except the # character

I want to split a string against the following characters
~!#$%^&*()_+­=<>,.?/:;"'{}|[]\, \n,\t, space
I tried to use \\s regex delimiter but i don't want the # included as the split character so that a string like this is #funny should result to this is #funny as the resulting values.
I have tried the following but it doesn't work.
this is #funny".split("\\s")
but it doesn't work. Any ideas?

Just specify the characters you want in square bracket, which means any of. Single escape Java characters (like \") and double escape Regex special characters (like \\[):
#Test
public void testName() throws Exception
{
String[] split = "this is #funny".split("[~!#$%^&*()_+­=<>,.?/:;\"'{}|\\[\\]\\\\ \\n\\t]");
for (String string : split)
{
logger.debug(string);
}
}

User replaceAll(String regex,String replacement) method from String.
String result = "this is #funny".replaceAll("[~!#$%^&*()_+­=<>,.?/:;\"'{}|\\[\\]\\,\\n\\t]", "");
System.out.println(result);

You can try to implement this:
String[] split = "this&is%a#funny^string".split("[^#\\p{Alnum}]|\\s+");
for (String string : split){
System.out.println(string);
}
Also check the Java API (Patterns) for more information on how to process strings.

It look like this will work for you:
String[] split = str.split("[^a-zA-Z&&[^#]]+");
This uses a character class subtraction to split on non-letter chars, except the hash.
Here's some test code:
String str = "this is #funny";
String[] split = str.split("[^a-zA-Z&&[^#]]+");
System.out.println(Arrays.toString(split));
Output:
[this, is, #funny]

How to replace part of a String in Java?

Im trying to replace part of a String based on a certain phrase being present within it. Consider the string "Hello my Dg6Us9k. I am alive.".
I want to search for the phase "my" and remove 8 characters to the right, which removes the hash code. This gives the string "Hello. I am alive." How can i do this in Java?

You could achieve this through string.replaceAll function.
string.replaceAll("\\bmy.{8}", "");
Add \\b if necessary. \\b called word boundary which matches between a word character and a non-word character. .{8} matches exactly the following 8 characters.
To remove also the space before my
System.out.println("Hello my Dg6Us9k. I am alive.".replaceAll("\\smy.{8}", ""));

This should do it:
String s = ("Hello my Dg6Us9k. I am alive");
s.replace(s.substring(s.indexOf("my"), s.indexOf("my")+11),"");
That is replacing the string starts at "my" and is 11 char long with nothing.

Use regex like this :
public static void main(String[] args) {
String s = "Hello my Dg6Us9k. I am alive";
String newString=s.replaceFirst("\\smy\\s\\w{7}", "");
System.out.println(newString);
}
O/P :
Hello. I am alive

Java strings are immutable, so you cannot change the string. You have to create a new string. So, find the index i of "my". Then concatenate the substring before (0...i) and after (i+8...).
int i = s.indexOf("my");
if (i == -1) { /* no "my" in there! */ }
string ret = s.substring(0,i);
ret.concat(s.substring(i+2+8));
return ret;

If you want to be flexible about the hash code length, use the folowing regexp:
String foo="Hello my Dg6Us9k. I am alive.";
String bar = foo.replaceFirst("\\smy.*?\\.", ".");
System.out.println(bar);

How to replace \ followed by letters in java String?

I need to delete all tokens that are started with \ and followed by any characters.
I created such a pattern:
input.replaceAll("\\[a-zA-Z0-9]*", "");
But it doesn't work because it doesn't delete \rad from string 5 4\rad.
EDIT:
public static void main(String[] args)
{
String input="Wolf 3 3\4par";
String replaceAll = input.replaceAll("\\\\[a-zA-Z0-9]*", "");
System.out.println("replaceAll=" + replaceAll);
}
Thank you!

The \ is special both in string literals and in regular expressions. To put an actual \ in a regular expression, you have to escape it twice. You also have to assign the result somewhere, which it wasn't clear from your question you were doing. So:
input = input.replaceAll("\\\\[a-zA-Z0-9]*", "");
Complete example: Live Copy
import java.util.*;
public class Temp {
public static void main(String[] args) {
String input = "4 5 \\rad";
input = input.replaceAll("\\\\[a-zA-Z0-9]*", "");
System.out.println(input);
}
}
Output:
4 5

To create \ literal in regex you need to pass \\ to regex engine. But to create \ literal in String you also have to escape it so you need to write it as "\\".
\ literal in regex engine
\\ regex pattern
"\\\\" String representing regex pattern
Now you are using one \ in your regex pattern regex engine sees it as \[ which escapes [ making it simple literal.
Try this way
input.replaceAll("\\\\[a-zA-Z0-9]*", "");

From
Sorry, but my String is exactly 5 4\rad. Indeed how to delete \rad? – Volodymyr Levytskyi
Try
String k= "5 4\rad";
System.out.println(k.replaceAll("\r\\w*", ""));
Output
5 4

How to insert backslash into my string in java?

I have string, and I want to replace one of its character with backslash \
I tried the following, but no luck.
engData.replace("'t", "\\'t")
and
engData = engData.replace("'t", String.copyValueOf(new char[]{'\\', 't'}));
INPUT : "can't"
EXPECTED OUTPUT : "can\'t"
Any idea how to do this?

Try this..
String s = "can't";
s = s.replaceAll("'","\\\\'");
System.out.println(s);
out put :
can\'t
This will replace every ' occurences with \' in your string.

Try like this
engData.replace("'", "\\\'");
INPUT : can't
EXPECTED OUTPUT : can\'t

String is immutable in Java. You need to assign back the modified string to itself.
engData = engData.replace("'t", "\\'t"); // assign the modified string back.

This is possible with regex:
engData = engData.replaceAll("('t)","\\\\$1");
The ( and ) specify a group. The 't will match any string containing 't. Finally, the second part replaced such a string with a backslash character: \\\\ (four because this), and the first group: $1. Thus you are replacing any substring 't with \'t
The same thing is possible without regex, what you tried (see this for output):
engData = engData.replace("'t","\\'t"); //note the assignment; Strings are immutable
See String.replace(CharSequence, CharSequence)

For String instances you can use, str.replaceAll() will return a new String with the changes requested:
String str = "./";
String s_modified = s.replaceAll("\\./", "");

The following works for me:
class Foobar {
public static void main(String[] args) {
System.err.println("asd\\'t".replaceAll("\\'t", "\\\'t"));
}
}