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Add escape "\" in front of special character for a string

I have a simple SQL query where I check whether the query matches any of the fields I have. I'm using LIKE statement for this. One of my field can have special characters and so does the search query. So I'm looking for a solution where I need to an escape "\" in front of the special character.
query = "hello+Search}query"
I need the above to change to
query = "hello\+Search\}query"
Is there a simple way of doing this other than searching for each special character separately and adding the "\". Because if I don't have the escape character I will get the error message
java.util.regex.PatternSyntaxException: Dangling meta character '+' near index 0
Thanks in advance

Decide which special characters you want to escape and just call
query.replace("}", "\\}")
You may keep all special characters you allow in some array then iterate it and replace the occurrences as exemplified.
This method replaces all regex meta characters.
public String escapeMetaCharacters(String inputString){
final String[] metaCharacters = {"\\","^","$","{","}","[","]","(",")",".","*","+","?","|","<",">","-","&","%"};
for (int i = 0 ; i < metaCharacters.length ; i++){
if(inputString.contains(metaCharacters[i])){
inputString = inputString.replace(metaCharacters[i],"\\"+metaCharacters[i]);
}
}
return inputString;
}
You could use it as query=escapeMetaCharacters(query);
Don't think that any library you would find would do anything more than that. At best it defines a complete list of specialCharacters.

There is actually a better way of doing this in a sleek manner.
String REGEX = "[\\[+\\]+:{}^~?\\\\/()><=\"!]";
StringUtils.replaceAll(inputString, REGEX, "\\\\$0");

You need to use \\ to introduce a \ into a string literal; that is you need to escape the \. (A single backslash is used to introduce special characters into a string: e.g. \t is a tab.)
query = "hello\\+Search\\}query" is what you need.

I had to do same thing in javascript. I came up with below solution. I think it might help someone.
function escapeSpecialCharacters(s){
let arr = s.split('');
arr = arr.map(function(d){
return d.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\'+d)
});
let reg = new RegExp(arr.join(''));
return reg;
}
let newstring = escapeSpecialCharacters("hello+Search}query");

If you want to use Java 8+ and Streams, you could do something like:
private String escapeSpecialCharacters(String input) {
List<String> specialCharacters = Lists.newArrayList("\\","^","$","{","}","[","]","(",")",".","*","+","?","|","<",">","-","&","%");
return Arrays.stream(input.split("")).map((c) -> {
if (specialCharacters.contains(c)) return "\\" + c;
else return c;
}).collect(Collectors.joining());
}

The simple version ( without deprecated StringUtils.replaceAll ):
String regex = "[\\[+\\]+:{}^~?\\\\/()><=\"!]";
String query = "hello+Search}query";
String replaceAll = query.replaceAll(regex, "\\\\$0");

Forcing newline to print correctly again

I had to export a bunch of strings to a CSV that I opened in excel. The strings contained '\n' and '\t' which I needed included in the CSV so I did the following before exporting the data:
public static String unEscapString(String s)
{
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++)
{
switch (s.charAt(i))
{
case '\n': sb.append("\\n"); break;
case '\t': sb.append("\\t"); break;
default: sb.append(s.charAt(i));
}
}
return sb.toString();
}
The problem is that I am now reimporting the data into Java but I can't figure out how to get the newline and tab to print correctly again. I've tried:
s.replaceAll("\\n", "\n");
but it still ignores the newlines. Help?
EDIT: Example of what i'm trying to do:
Say one string in the CSV is "foo \n bar". When I import it using Java and i'm trying to print the same string to the console but have the newline behave correctly

replaceAll's first argument is a regular expression. You have 2 choices. You can use plain old replace like so:
s.replace("\\n", "\n");
or you can escape the slash for the regex parser (which is stripping the single slash out):
s.replaceAll("\\\\n", "\n");
or
s.replaceAll(Pattern.quote("\\n"), "\n");
I would opt for replace since you're not using a regular expression.

It should be
sb.append("\n");
Otherwise, you will get a '\' and a 'n' by using "\\n".
But I recommend you to use:
sb.append(System.getProperty("line.separator"));
Here System.getProperty("line.separator") gives you platform independent newline in java. Also from Java 7 there's a method that returns the value directly: System.lineSeparator().

If you want an actual newline in the string, it should be \n, not \\n. The way you have it, it is being interpreted as a backslash and then an 'n'.

How to use replace(char, char) to replace all instances of character b with nothing

How do i use replace(char, char) to replace all instances of character "b" with nothing.
For example:
Hambbburger to Hamurger
EDIT: Constraint is only JDK 1.4.2, meaning no overloaded version of replace!

There's also a replaceAll function that uses strings, note however that it evals them as regexes, but for replacing a single char will do just fine.
Here's an example:
String meal = "Hambbburger";
String replaced = meal.replaceAll("b","");
Note that the replaced variable is necessary since replaceAll doesn't change the string in place but creates a new one with the replacement (String is immutable in java).
If the character you want to replace has a different meaning in a regex (e.g. the . char will match any char, not a dot) you'll need to quote the first parameter like this:
String meal = "Ham.bur.ger";
String replaced = meal.replaceAll(Pattern.quote("."),"");

Strings are immutable, so make sure you assign the result to a string.
String str = "Hambbburger";
str = str.replace("b", "");
You don't need replaceAll if you use Java 6. See here: replace

Try this code....
public class main {
public static void main(String args[]){
String g="Hambbburger.i want to eat Hambbburger. ";
System.out.print(g);
g=g.replaceAll("b", "");
System.out.print("---------After Replacement-----\n");
System.out.print(g);
}
}
output
Hambbburger.i want to eat Hambbburger. ---------After Replacement-----
Hamurger.i want to eat Hamurger.

String text = "Hambbburger";
text = text.replace('b', '\0');
The '\0' represents NUL in ASCII code.

replaceAll in String doesnot work properly .It's Always recomend to use replace()
Ex:-
String s="abcdefabcdef";
s=s.replace("a","");

String str="aabbcc";
int n=str.length();
char ch[]=str.toCharArray();
for(int i=0;i<n-1;i++)
{
for(int j=i+1;j<n;j++)
{
if(ch[i]==ch[j])
{
ch[j]='*';
}
}
}
String temp=new String(ch);
for(int i=0;i<temp.length();i++)
{
if(temp.charAt(i)!='*')
System.out.print(temp.charAt(i));
}

Java how can I add an accented "e" to a string?

With the help of tucuxi from the existing post Java remove HTML from String without regular expressions I have built a method that will parse out any basic HTML tags from a string. Sometimes, however, the original string contains html hexadecimal characters like &#x00E9 (which is an accented e). I have started to add functionality which will translate these escaped characters into real characters.
You're probably asking: Why not use regular expressions? Or a third party library? Unfortunately I cannot, as I am developing on a BlackBerry platform which does not support regular expressions and I have never been able to successfully add a third party library to my project.
So, I have gotten to the point where any &#x00E9 is replaced with "e". My question now is, how do I add an actual 'accented e' to a string?
Here is my code:
public static String removeHTML(String synopsis) {
char[] cs = synopsis.toCharArray();
String sb = new String();
boolean tag = false;
for (int i = 0; i < cs.length; i++) {
switch (cs[i]) {
case '<':
if (!tag) {
tag = true;
break;
}
case '>':
if (tag) {
tag = false;
break;
}
case '&':
char[] copyTo = new char[7];
System.arraycopy(cs, i, copyTo, 0, 7);
String result = new String(copyTo);
if (result.equals("&#x00E9")) {
sb += "e";
}
i += 7;
break;
default:
if (!tag)
sb += cs[i];
}
}
return sb.toString();
}
Thanks!

Java Strings are unicode.
sb += '\u00E9'; # lower case e + '
sb += '\u00C9'; # upper case E + '

You can print out just about any character you like in Java as it uses the Unicode character set.
To find the character you want take a look at the charts here:
http://www.unicode.org/charts/
In the Latin Supplement document you'll see all the unicode numbers for the accented characters. You should see the hex number 00E9 listed for é for example. The numbers for all Latin accented characters are in this document so you should find this pretty useful.
To print use character in a String, just use the Unicode escape sequence of \u followed by the character code like so:
System.out.print("Let's go to the caf\u00E9");
Would produce: "Let's go to the café"
Depending in which version of Java you're using you might find StringBuilders (or StringBuffers if you're multi-threaded) more efficient than using the + operator to concatenate Strings too.

try this:
if (result.equals("&#x00E9")) {
sb += char(130);
}
instead of
if (result.equals("&#x00E9")) {
sb += "e";
}
The thing is that you're not adding an accent to the top of the 'e' character, but rather that is a separate character all together. This site lists out the ascii codes for characters.

For a table of accented in characters in Java take a look at this reference.
To decode the html part, use Apache StringEscapeUtils from Apache commons lang:
import org.apache.commons.lang.StringEscapeUtils;
...
String withCharacters = StringEscapeUtils.unescapeHtml(yourString);
See also this Stack Overflow thread:
Replace HTML codes with equivalent characters in Java

How do I replace a character in a string in Java?

Using Java, I want to go through the lines of a text and replace all ampersand symbols (&) with the XML entity reference &.
I scan the lines of the text and then each word in the text with the Scanner class. Then I use the CharacterIterator to iterate over each characters of the word. However, how can I replace the character? First, Strings are immutable objects. Second, I want to replace a character (&) with several characters(amp&;). How should I approach this?
CharacterIterator it = new StringCharacterIterator(token);
for(char ch = it.first(); ch != CharacterIterator.DONE; ch = it.next()) {
if(ch == '&') {
}
}

Try using String.replace() or String.replaceAll() instead.
String my_new_str = my_str.replace("&", "&");
(Both replace all occurrences; replaceAll allows use of regex.)

The simple answer is:
token = token.replace("&", "&");
Despite the name as compared to replaceAll, replace does do a replaceAll, it just doesn't use a regular expression, which seems to be in order here (both from a performance and a good practice perspective - don't use regular expressions by accident as they have special character requirements which you won't be paying attention to).
Sean Bright's answer is probably as good as is worth thinking about from a performance perspective absent some further target requirement on performance and performance testing, if you already know this code is a hot spot for performance, if that is where your question is coming from. It certainly doesn't deserve the downvotes. Just use StringBuilder instead of StringBuffer unless you need the synchronization.
That being said, there is a somewhat deeper potential problem here. Escaping characters is a known problem which lots of libraries out there address. You may want to consider wrapping the data in a CDATA section in the XML, or you may prefer to use an XML library (including the one that comes with the JDK now) to actually generate the XML properly (so that it will handle the encoding).
Apache also has an escaping library as part of Commons Lang.

StringBuilder s = new StringBuilder(token.length());
CharacterIterator it = new StringCharacterIterator(token);
for (char ch = it.first(); ch != CharacterIterator.DONE; ch = it.next()) {
switch (ch) {
case '&':
s.append("&");
break;
case '<':
s.append("<");
break;
case '>':
s.append(">");
break;
default:
s.append(ch);
break;
}
}
token = s.toString();

You may also want to check to make sure your not replacing an occurrence that has already been replaced. You can use a regular expression with negative lookahead to do this.
For example:
String str = "sdasdasa&adas&dasdasa";
str = str.replaceAll("&(?!amp;)", "&");
This would result in the string "sdasdasa&adas&dasdasa".
The regex pattern "&(?!amp;)" basically says: Match any occurrence of '&' that is not followed by 'amp;'.

Just create a string that contains all of the data in question and then use String.replaceAll() like below.
String result = yourString.replaceAll("&", "&");

You can use stream and flatMap to map & to &
String str = "begin&end";
String newString = str.chars()
.flatMap(ch -> (ch == '&') ? "&".chars() : IntStream.of(ch))
.collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
.toString();

Escaping strings can be tricky - especially if you want to take unicode into account. I suppose XML is one of the simpler formats/languages to escape but still. I would recommend taking a look at the StringEscapeUtils class in Apache Commons Lang, and its handy escapeXml method.

Try this code.You can replace any character with another given character.
Here I tried to replace the letter 'a' with "-" character for the give string "abcdeaa"
OutPut -->_bcdef__
public class Replace {
public static void replaceChar(String str,String target){
String result = str.replaceAll(target, "_");
System.out.println(result);
}
public static void main(String[] args) {
replaceChar("abcdefaa","a");
}
}

If you're using Spring you can simply call HtmlUtils.htmlEscape(String input) which will handle the '&' to '&' translation.

//I think this will work, you don't have to replace on the even, it's just an example.
public void emphasize(String phrase, char ch)
{
char phraseArray[] = phrase.toCharArray();
for(int i=0; i< phrase.length(); i++)
{
if(i%2==0)// even number
{
String value = Character.toString(phraseArray[i]);
value = value.replace(value,"*");
phraseArray[i] = value.charAt(0);
}
}
}

String taskLatLng = task.getTask_latlng().replaceAll( "\\(","").replaceAll("\\)","").replaceAll("lat/lng:", "").trim();