Trim characters in Java

Question

How can I trim characters in Java?
e.g.

String j = “\joe\jill\”.Trim(new char[] {“\”});

j should be

"joe\jill"

String j = “jack\joe\jill\”.Trim("jack");

j should be

"\joe\jill\"

etc

Answer 1

Apache Commons has a great StringUtils class (org.apache.commons.lang.StringUtils). In StringUtils there is a strip(String, String) method that will do what you want.

I highly recommend using Apache Commons anyway, especially the Collections and Lang libraries.

Answer 2

This does what you want:

public static void main (String[] args) {
    String a = "\\joe\\jill\\";
    String b = a.replaceAll("\\\\$", "").replaceAll("^\\\\", "");
    System.out.println(b);
}

The $ is used to remove the sequence in the end of string. The ^ is used to remove in the beggining.

As an alternative, you can use the syntax:

String b = a.replaceAll("\\\\$|^\\\\", "");

The | means "or".

In case you want to trim other chars, just adapt the regex:

String b = a.replaceAll("y$|^x", ""); // will remove all the y from the end and x from the beggining

Answer 3

it appears that there is no ready to use java api that makes that but you can write a method to do that for you. this link might be usefull

Answer 4

CharMatcher – Google Guava

In the past, I'd second Colins’ Apache commons-lang answer. But now that Google’s guava-libraries is released, the CharMatcher class will do what you want quite nicely:

String j = CharMatcher.is('\\').trimFrom("\\joe\\jill\\"); 
// j is now joe\jill

CharMatcher has a very simple and powerful set of APIs as well as some predefined constants which make manipulation very easy. For example:

CharMatcher.is(':').countIn("a:b:c"); // returns 2
CharMatcher.isNot(':').countIn("a:b:c"); // returns 3
CharMatcher.inRange('a', 'b').countIn("a:b:c"); // returns 2
CharMatcher.DIGIT.retainFrom("a12b34"); // returns "1234"
CharMatcher.ASCII.negate().removeFrom("a®¶b"); // returns "ab";

Very nice stuff.

Answer 5

Here is another non-regexp, non-super-awesome, non-super-optimized, however very easy to understand non-external-lib solution:

public static String trimStringByString(String text, String trimBy) {
    int beginIndex = 0;
    int endIndex = text.length();

    while (text.substring(beginIndex, endIndex).startsWith(trimBy)) {
        beginIndex += trimBy.length();
    } 

    while (text.substring(beginIndex, endIndex).endsWith(trimBy)) {
        endIndex -= trimBy.length();
    }

    return text.substring(beginIndex, endIndex);
}

Usage:

String trimmedString = trimStringByString(stringToTrim, "/");

Answer 6

Hand made for the first option:

public class Rep {
    public static void main( String [] args ) {
       System.out.println( trimChar( '\\' , "\\\\\\joe\\jill\\\\\\\\" )  ) ;
       System.out.println( trimChar( '\\' , "joe\\jill" )  ) ;
    }
    private static String trimChar( char toTrim, String inString ) { 
        int from = 0;
        int to = inString.length();

        for( int i = 0 ; i < inString.length() ; i++ ) {
            if( inString.charAt( i ) != toTrim) {
                from = i;
                break;
            }
        }
        for( int i = inString.length()-1 ; i >= 0 ; i-- ){ 
            if( inString.charAt( i ) != toTrim ){
                to = i;
                break;
            }
        }
        return inString.substring( from , to );
    }
}

Prints

joe\jil

joe\jil