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Replacing multiple substrings in Java when replacement text overlaps search text

Say you have the following line:

cat dog fish dog fish cat

You want to replace everything catswith dogs, everything dogswith fishand everything fishwith cats. Intuitively expected result:

dog fish cat fish cat dog

If you try to find the obvious solution by going through replaceAll(), you will get:

  • (original) cat dog fish dog fish cat
  • (cat → dog) dog dog fish dog fish dog
  • (dog → fish) fish fish fish fish fish fish
  • (fish → cat) cat cat cat cat cat cat

Clearly, this is not the intended result. So what is the easiest way to do this? I can cobble something together with Patternand Matcher(and a lot of Pattern.quote()and Matcher.quoteReplacement()), but I refuse to believe that I am the first person who has this problem, and there is no library function to solve it,

(FWIW, the actual case is a little more complicated and does not require direct swaps.)

+5
4

, StringUtils.replaceEach apache commons , :

StringUtils.replaceEach("abcdeab", new String[]{"ab", "cd"}, new String[]{"cd", "ab"});
// returns "cdabecd"

, . . .

+8
String rep = str.replace("cat","§1§").replace("dog","§2§")
                .replace("fish","§3§").replace("§1§","dog")
                .replace("§2§","fish").replace("§3§","cat");

, , .

, . , . , , ( ). , :

public static String replace(
    final String input, final Map<String, String> replacements) {

    if (input == null || "".equals(input) || replacements == null 
        || replacements.isEmpty()) {
        return input;
    }
    StringBuilder regexBuilder = new StringBuilder();
    Iterator<String> it = replacements.keySet().iterator();
    regexBuilder.append(Pattern.quote(it.next()));
    while (it.hasNext()) {
        regexBuilder.append('|').append(Pattern.quote(it.next()));
    }
    Matcher matcher = Pattern.compile(regexBuilder.toString()).matcher(input);
    StringBuffer out = new StringBuffer(input.length() + (input.length() / 10));
    while (matcher.find()) {
        matcher.appendReplacement(out, replacements.get(matcher.group()));
    }
    matcher.appendTail(out);
    return out.toString();
}

:

System.out.println(replace("cat dog fish dog fish cat",
    ImmutableMap.of("cat", "dog", "dog", "fish", "fish", "cat")));

:

, , .

+7

StringBuilder, , , , . , .

, , - :

// pseudocode
text is new text swapping cat with dog
text is new text swapping dog with fish
text is new text swapping fish with cat


for each word in text
   if word is cat, swap with dog
   if word is dog, swap with fish
   if word is fish, swap with cat
   transfer new word (or unchanged word) into StringBuilder.

, , swap (...) HashMap .

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class SwapWords {
   private static Map<String, String> myMap = new HashMap<String, String>();

   public static void main(String[] args) {
      // this would really be loaded using a file such as a text file or xml
      // or even a database:
      myMap.put("cat", "dog");
      myMap.put("dog", "fish");
      myMap.put("fish", "dog");

      String testString = "cat dog fish dog fish cat";

      StringBuilder sb = new StringBuilder();
      Scanner testScanner = new Scanner(testString);
      while (testScanner.hasNext()) {
         String text = testScanner.next();
         text = myMap.get(text) == null ? text : myMap.get(text);
         sb.append(text + " ");
      }

      System.out.println(sb.toString().trim());
   }
}
+4
public class myreplase {
    public Map<String, String> replase;

    public myreplase() {
        replase = new HashMap<String, String>();

        replase.put("a", "Apple");
        replase.put("b", "Banana");
        replase.put("c", "Cantalope");
        replase.put("d", "Date");
        String word = "a b c d a b c d";

        String ss = "";
        Iterator<String> i = replase.keySet().iterator();
        while (i.hasNext()) {
            ss += i.next();
            if (i.hasNext()) {
                ss += "|";
            }
        }

        Pattern pattern = Pattern.compile(ss);
        StringBuilder buffer = new StringBuilder();
        for (int j = 0, k = 1; j < word.length(); j++,k++) {
            String s = word.substring(j, k);
            Matcher matcher = pattern.matcher(s);
            if (matcher.find()) {
                buffer.append(replase.get(s));
            } else {
                buffer.append(s);
            }
        }
        System.out.println(buffer.toString());
    }

    public static void main(String[] args) {
        new myreplase();
    }
}

: - Apple Banana Cantalope Date Apple Banana Cantalope Date

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