How to remove duplicate white spaces in string using Java?

Like this:

yourString = yourString.replaceAll("\\s+", " ");

For example

System.out.println("lorem  ipsum   dolor \n sit.".replaceAll("\\s+", " "));

outputs

lorem ipsum dolor sit.

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What does that \s+ mean?

\s+ is a regular expression. \s matches a space, tab, new line, carriage return, form feed or vertical tab, and + says "one or more of those". Thus the above code will collapse all "whitespace substrings" longer than one character, with a single space character.

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Source: Java: Removing duplicate white spaces in strings

Try this - You have to import java.util.regex.*;

    Pattern pattern = Pattern.compile("\\s+");
    Matcher matcher = pattern.matcher(string);
    boolean check = matcher.find();
    String str = matcher.replaceAll(" ");

Where string is your string on which you need to remove duplicate white spaces

String str = "   Text    with    multiple    spaces    ";
str = org.apache.commons.lang3.StringUtils.normalizeSpace(str);
// str = "Text with multiple spaces"

You can use the regex

(\s)\1

and

replace it with $1.

Java code:

str = str.replaceAll("(\\s)\\1","$1");

If the input is "foo\t\tbar " you'll get "foo\tbar " as output
But if the input is "foo\t bar" it will remain unchanged because it does not have any consecutive whitespace characters.

If you treat all the whitespace characters(space, vertical tab, horizontal tab, carriage return, form feed, new line) as space then you can use the following regex to replace any number of consecutive white space with a single space:

str = str.replaceAll("\\s+"," ");

But if you want to replace two consecutive white space with a single space you should do:

str = str.replaceAll("\\s{2}"," ");