How to replace specific characters in a String with different ones?

Question

Given a

String text = "RHKKA";

How to efficiently replace all 'R' with 'H', all 'H' with 'E', all 'K' with 'L' and all 'A' with 'O'?

String text would be HELLO then.

Answer 1

You can create a Map of Character as key and value, then loop over character by character like so :

String text = "RHKKA";
Map<Character, Character> map = new HashMap<>();
map.put('R', 'H');
map.put('H', 'E');
map.put('K', 'L');
map.put('A', 'O');
char[] chars = text.toCharArray();
for (int i = 0; i < chars.length; i++) {
    chars[i] = map.get(chars[i]);
}
String result = String.valueOf(chars);
System.out.println(result.toString());//HELLO

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Java8+ possible solution

Or if you are using Java8+ you can use :

String result = text.chars()
        .mapToObj(c -> String.valueOf(map.get((char) c)))
        .collect(Collectors.joining());//HELLO

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Java9+ possible solution

Another possible solution if to use Matcher::replaceAll like so :

String text = "RHKKA";
Map<Character, Character> map = Map.of('R', 'H', 'H', 'E', 'K', 'L', 'A', 'O');
text = Pattern.compile(".").matcher(text)
        .replaceAll(c -> String.valueOf(map.get(c.group().charAt(0))));//HELLO

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You can read more about Map.of