我想在Java中使用String.replaceAll（regex，regex）而不是（regex，String）

Question

Example:

input = "10N10N";
input = input.replaceAll("1|N", "N|1"); // syntax not correct

expected output: N01N01

What I'm asking is for a single-lined iterator that replaces all "1" with "N" and all "N" with "1".

Answer 1

Since Java 9 Matcher class contains replaceAll​(Function<MatchResult,String> replacer) where you can specify dynamically what should be used as replacement based on current match. So your code may look like:

Map<String, String> replacementsMap = Map.ofEntries(
        Map.entry("1", "N"),
        Map.entry("N", "1")
);

String input = "10N10N";
Pattern p = Pattern.compile("1|N");
Matcher m = p.matcher(input);
String replaced = m.replaceAll(match -> replacementsMap.get(match.group()));
System.out.println(replaced);

Output: N01N01 .

---

In pre Java 9 you can use Matcher#appendReplacement and Matcher#appendTail instead of replaceAll like

//create Pattern p, Matcher m and replacement map
StringBuffer sb = new StringBuffer();
while(m.find()){
    m.appendReplacement(sb, replacementsMap.get(m.group()));
}
m.appendTail(sb);
String replaced = sb.toString();

---

If you are willing to use external libraries then Apache Commons - Lang include StringUtils class with replaceEach(String text, String[] searchList, String[] replacementList) method. You can use it like:

String input = "10N10N";
String replaced = StringUtils.replaceEach(input, new String[] {"1","N"}, new String[] {"N","1"});
System.out.println(replaced);//N01N01

Answer 2

I'd advise you to prefer not going the regex way. Instead, why not go this way:

• Replace all 1 with _ (OR any not-present char in the input string), then replace N by 1, and further replace _ by N.

This can be easily done by multiple replaces, all within a single line.

Answer 3

Try to use :

input = input.replace("1", "-")//replace all 1 by - 
        .replace("N", "1")     //replace all N by 1
        .replace("-", "N");    //replace all - by N

More secure solution, if you are using Java 8 you can use :

String result = input.chars()
        .map(x -> x == 'N' ? '1' : x == '1' ? 'N' : x)
        .collect(StringBuilder::new,
                StringBuilder::appendCodePoint,
                StringBuilder::append
        ).toString();

Output

N01N01