Java String. Replace list of chars by other chars list

Question

I have String variable with value- f.e.: this is test-str-ing_łóśżćń.

And I would like replace this chars:

, -, ł,ó,ś,ż,ć,ń with those:

_,_,l,o,s,z,c,n.

And I mean here, that if parser will found f.e.: char - (which is second in first list) should be replaced with char that is in the same position/place in second list, which in this example is: _.

The char ó should be replaced with char o.

The char ń should be replaced with char n.

In my case the list of characters to replace is quite long and parsing in loop for each char to replace would not be enought efficient.

I know method replaceAll(). but it only accept one in String and one out String

So I am looking for method, that will allow me to work on arrays/list of Strings instead of single String.

Please give me some help.

I suggest you give a shot at apache commons lang & StringUtils commons.apache.org/proper/commons-lang/apidocs/org/apache/… — dotvav
– dotvav, Commented Sep 16, 2015 at 9:35
replaceAll is heavy weight (regex). fast is replace() with few variants. — Jacek Cz
– Jacek Cz, Commented Sep 16, 2015 at 9:36
professional seems implement "codepage" operations with CharsetProvider and family. I saw something for ancient polish pages 852, mazovia and converters. — Jacek Cz
– Jacek Cz, Commented Sep 16, 2015 at 9:39
Have a look at the question linked by dasblinkenlight. I have the strong feeling that that's what you're after. Add a second call to replaceAll and replace spaces, minuses etc. with an underscore. — Thomas
– Thomas, Commented Sep 16, 2015 at 9:47

Joop Eggen · Accepted Answer · 2015-09-16 09:48:51Z

4

Use java.text.Normalizer to Decompose accented letters in base letter plus "combining diacritical marks."

String base = Normalizer.normalize(accented, Form.NFKD)
    .replaceAll("\\p{M}", "");

This does a decompose (D) normalization, and then removes Marks.

Some replacements still needed.

answered Sep 16, 2015 at 9:48

Joop Eggen

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5 Comments

masterdany88 Over a year ago

Ok. I will give it a try, cause seems to be most elegant proposition.

masterdany88 Over a year ago

Tested. It doesn't convert ł to l, and still need to change space to _

masterdany88 Over a year ago

I've added some extra replaceAll to achieve my goal:

return Normalizer.normalize(stringToConvert,Form.NFKD).replaceAll("\\p{M}", "").replaceAll(" ", "_").replaceAll("ł", "l");

. Now it works. Thanks.

Joop Eggen Over a year ago

It would suffice to do .replace("ł", "l") maybe even .replace(' ', '_') without the regex overhead.

RokL Over a year ago

The string replace is faster than regex replace and the char replace is faster than string replace since the new string length is known ahead of time.

Jacek Cz · Accepted Answer · 2015-09-16 09:50:46Z

1

    char[] out = new char[src.length()];
    for( j ...){
    inputChar = src.charAt(j);
    for (int i = 0; i < convertChars.length; i++) {
       if (inputChar == convertChars[i]) {
         inputChar = toChars[i];
       }
     }
    }
     out[j] = inputChar ;
   }
    out2 = new String(out);

Extracted from bigger code without IDE, not tested. Loop (I hope) don't allocate objects and should not degrade speed.

edited Sep 16, 2015 at 9:50

answered Sep 16, 2015 at 9:45

Jacek Cz

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RokL · Accepted Answer · 2015-09-16 09:59:14Z

0

Make a static lookup table:

private static char[] substitutions = new char[65536];
static {
    // Initialize
    for (char c = 0; c < substitutions.length; c++) {
        substitutions[c] = c;
    }
    // Now add mappings.
    substitions['-'] = '_'; // Map source->target character
    ... // Add the rest
}
// LATER IN Code
char[] stringChars = inputString.toCharArray();
for (int i = 0; i < stringChars.length; i++) {
    stringChars[i] = substitutions[stringChars[i]];
}
outputString = new String(stringChars);

answered Sep 16, 2015 at 9:59

RokL

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2 Comments

Jacek Cz Over a year ago

Probably on of the fastest algorithms (what with RAM? maybe isn't problem?) I had used this technique extensively in "C", DOS times, substitutions equivalent had 256B, highly optimizing C compiler does basic operation in 2-3 CPU cycles.

RokL Over a year ago

That array is 128kb which is nothing on today's machines.

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